lib.rs

// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

// Support code for rustc's built in test runner generator. Currently,
// none of this is meant for users. It is intended to support the
// simplest interface possible for representing and running tests
// while providing a base that other test frameworks may build off of.

#[crate_id = "test#0.10-pre"];
#[comment = "Rust internal test library only used by rustc"];
#[license = "MIT/ASL2"];
#[crate_type = "rlib"];
#[crate_type = "dylib"];

#[feature(asm)];

extern crate collections;
extern crate extra;
extern crate getopts;
extern crate serialize;
extern crate term;

use collections::TreeMap;
use extra::json::ToJson;
use extra::json;
use extra::stats::Stats;
use extra::stats;
use extra::time::precise_time_ns;
use getopts::{OptGroup, optflag, optopt};
use serialize::Decodable;
use term::Terminal;
use term::color::{Color, RED, YELLOW, GREEN, CYAN};

use std::cmp;
use std::io;
use std::io::{File, PortReader, ChanWriter};
use std::io::stdio::StdWriter;
use std::str;
use std::task;
use std::to_str::ToStr;
use std::f64;
use std::os;

// to be used by rustc to compile tests in libtest
pub mod test {
    pub use {BenchHarness, TestName, TestResult, TestDesc,
             TestDescAndFn, TestOpts, TrFailed, TrIgnored, TrOk,
             Metric, MetricMap, MetricAdded, MetricRemoved,
             MetricChange, Improvement, Regression, LikelyNoise,
             StaticTestFn, StaticTestName, DynTestName, DynTestFn,
             run_test, test_main, test_main_static, filter_tests,
             parse_opts};
}

// The name of a test. By convention this follows the rules for rust
// paths; i.e. it should be a series of identifiers separated by double
// colons. This way if some test runner wants to arrange the tests
// hierarchically it may.

#[deriving(Clone)]
pub enum TestName {
    StaticTestName(&'static str),
    DynTestName(~str)
}
impl ToStr for TestName {
    fn to_str(&self) -> ~str {
        match (*self).clone() {
            StaticTestName(s) => s.to_str(),
            DynTestName(s) => s.to_str()
        }
    }
}

#[deriving(Clone)]
enum NamePadding { PadNone, PadOnLeft, PadOnRight }

impl TestDesc {
    fn padded_name(&self, column_count: uint, align: NamePadding) -> ~str {
        use std::num::Saturating;
        let name = self.name.to_str();
        let fill = column_count.saturating_sub(name.len());
        let pad = " ".repeat(fill);
        match align {
            PadNone => name,
            PadOnLeft => pad.append(name),
            PadOnRight => name.append(pad),
        }
    }
}

/// Represents a benchmark function.
pub trait TDynBenchFn {
    fn run(&self, harness: &mut BenchHarness);
}

// A function that runs a test. If the function returns successfully,
// the test succeeds; if the function fails then the test fails. We
// may need to come up with a more clever definition of test in order
// to support isolation of tests into tasks.
pub enum TestFn {
    StaticTestFn(extern fn()),
    StaticBenchFn(extern fn(&mut BenchHarness)),
    StaticMetricFn(proc(&mut MetricMap)),
    DynTestFn(proc()),
    DynMetricFn(proc(&mut MetricMap)),
    DynBenchFn(~TDynBenchFn)
}

impl TestFn {
    fn padding(&self) -> NamePadding {
        match self {
            &StaticTestFn(..)   => PadNone,
            &StaticBenchFn(..)  => PadOnRight,
            &StaticMetricFn(..) => PadOnRight,
            &DynTestFn(..)      => PadNone,
            &DynMetricFn(..)    => PadOnRight,
            &DynBenchFn(..)     => PadOnRight,
        }
    }
}

// Structure passed to BenchFns
pub struct BenchHarness {
    priv iterations: u64,
    priv ns_start: u64,
    priv ns_end: u64,
    bytes: u64
}

// The definition of a single test. A test runner will run a list of
// these.
#[deriving(Clone)]
pub struct TestDesc {
    name: TestName,
    ignore: bool,
    should_fail: bool
}

pub struct TestDescAndFn {
    desc: TestDesc,
    testfn: TestFn,
}

#[deriving(Clone, Encodable, Decodable, Eq)]
pub struct Metric {
    priv value: f64,
    priv noise: f64
}

impl Metric {
    pub fn new(value: f64, noise: f64) -> Metric {
        Metric {value: value, noise: noise}
    }
}

#[deriving(Eq)]
pub struct MetricMap(TreeMap<~str,Metric>);

impl Clone for MetricMap {
    fn clone(&self) -> MetricMap {
        let MetricMap(ref map) = *self;
        MetricMap(map.clone())
    }
}

/// Analysis of a single change in metric
#[deriving(Eq)]
pub enum MetricChange {
    LikelyNoise,
    MetricAdded,
    MetricRemoved,
    Improvement(f64),
    Regression(f64)
}

pub type MetricDiff = TreeMap<~str,MetricChange>;

// The default console test runner. It accepts the command line
// arguments and a vector of test_descs.
pub fn test_main(args: &[~str], tests: ~[TestDescAndFn]) {
    let opts =
        match parse_opts(args) {
            Some(Ok(o)) => o,
            Some(Err(msg)) => fail!("{}", msg),
            None => return
        };
    match run_tests_console(&opts, tests) {
        Ok(true) => {}
        Ok(false) => fail!("Some tests failed"),
        Err(e) => fail!("io error when running tests: {}", e),
    }
}

// A variant optimized for invocation with a static test vector.
// This will fail (intentionally) when fed any dynamic tests, because
// it is copying the static values out into a dynamic vector and cannot
// copy dynamic values. It is doing this because from this point on
// a ~[TestDescAndFn] is used in order to effect ownership-transfer
// semantics into parallel test runners, which in turn requires a ~[]
// rather than a &[].
pub fn test_main_static(args: &[~str], tests: &[TestDescAndFn]) {
    let owned_tests = tests.map(|t| {
        match t.testfn {
            StaticTestFn(f) =>
            TestDescAndFn { testfn: StaticTestFn(f), desc: t.desc.clone() },

            StaticBenchFn(f) =>
            TestDescAndFn { testfn: StaticBenchFn(f), desc: t.desc.clone() },

            _ => {
                fail!("non-static tests passed to test::test_main_static");
            }
        }
    });
    test_main(args, owned_tests)
}

pub struct TestOpts {
    filter: Option<~str>,
    run_ignored: bool,
    run_tests: bool,
    run_benchmarks: bool,
    ratchet_metrics: Option<Path>,
    ratchet_noise_percent: Option<f64>,
    save_metrics: Option<Path>,
    test_shard: Option<(uint,uint)>,
    logfile: Option<Path>
}

/// Result of parsing the options.
pub type OptRes = Result<TestOpts, ~str>;

fn optgroups() -> ~[getopts::OptGroup] {
    ~[getopts::optflag("", "ignored", "Run ignored tests"),
      getopts::optflag("", "test", "Run tests and not benchmarks"),
      getopts::optflag("", "bench", "Run benchmarks instead of tests"),
      getopts::optflag("h", "help", "Display this message (longer with --help)"),
      getopts::optopt("", "save-metrics", "Location to save bench metrics",
                     "PATH"),
      getopts::optopt("", "ratchet-metrics",
                     "Location to load and save metrics from. The metrics \
                      loaded are cause benchmarks to fail if they run too \
                      slowly", "PATH"),
      getopts::optopt("", "ratchet-noise-percent",
                     "Tests within N% of the recorded metrics will be \
                      considered as passing", "PERCENTAGE"),
      getopts::optopt("", "logfile", "Write logs to the specified file instead \
                          of stdout", "PATH"),
      getopts::optopt("", "test-shard", "run shard A, of B shards, worth of the testsuite",
                     "A.B")]
}

fn usage(binary: &str, helpstr: &str) {
    let message = format!("Usage: {} [OPTIONS] [FILTER]", binary);
    println!("{}", getopts::usage(message, optgroups()));
    println!("");
    if helpstr == "help" {
        println!("{}", "\
The FILTER is matched against the name of all tests to run, and if any tests
have a substring match, only those tests are run.

By default, all tests are run in parallel. This can be altered with the
RUST_TEST_TASKS environment variable when running tests (set it to 1).

Test Attributes:

    #[test]        - Indicates a function is a test to be run. This function
                     takes no arguments.
    #[bench]       - Indicates a function is a benchmark to be run. This
                     function takes one argument (test::BenchHarness).
    #[should_fail] - This function (also labeled with #[test]) will only pass if
                     the code causes a failure (an assertion failure or fail!)
    #[ignore]      - When applied to a function which is already attributed as a
                     test, then the test runner will ignore these tests during
                     normal test runs. Running with --ignored will run these
                     tests. This may also be written as #[ignore(cfg(...))] to
                     ignore the test on certain configurations.");
    }
}

// Parses command line arguments into test options
pub fn parse_opts(args: &[~str]) -> Option<OptRes> {
    let args_ = args.tail();
    let matches =
        match getopts::getopts(args_, optgroups()) {
          Ok(m) => m,
          Err(f) => return Some(Err(f.to_err_msg()))
        };

    if matches.opt_present("h") { usage(args[0], "h"); return None; }
    if matches.opt_present("help") { usage(args[0], "help"); return None; }

    let filter =
        if matches.free.len() > 0 {
            Some((matches).free[0].clone())
        } else {
            None
        };

    let run_ignored = matches.opt_present("ignored");

    let logfile = matches.opt_str("logfile");
    let logfile = logfile.map(|s| Path::new(s));

    let run_benchmarks = matches.opt_present("bench");
    let run_tests = ! run_benchmarks ||
        matches.opt_present("test");

    let ratchet_metrics = matches.opt_str("ratchet-metrics");
    let ratchet_metrics = ratchet_metrics.map(|s| Path::new(s));

    let ratchet_noise_percent = matches.opt_str("ratchet-noise-percent");
    let ratchet_noise_percent = ratchet_noise_percent.map(|s| from_str::<f64>(s).unwrap());

    let save_metrics = matches.opt_str("save-metrics");
    let save_metrics = save_metrics.map(|s| Path::new(s));

    let test_shard = matches.opt_str("test-shard");
    let test_shard = opt_shard(test_shard);

    let test_opts = TestOpts {
        filter: filter,
        run_ignored: run_ignored,
        run_tests: run_tests,
        run_benchmarks: run_benchmarks,
        ratchet_metrics: ratchet_metrics,
        ratchet_noise_percent: ratchet_noise_percent,
        save_metrics: save_metrics,
        test_shard: test_shard,
        logfile: logfile
    };

    Some(Ok(test_opts))
}

pub fn opt_shard(maybestr: Option<~str>) -> Option<(uint,uint)> {
    match maybestr {
        None => None,
        Some(s) => {
            let vector = s.split('.').to_owned_vec();
            if vector.len() == 2 {
                match (from_str::<uint>(vector[0]),
                       from_str::<uint>(vector[1])) {
                    (Some(a), Some(b)) => Some((a, b)),
                    _ => None
                }
            } else {
                None
            }
        }
    }
}


#[deriving(Clone, Eq)]
pub struct BenchSamples {
    priv ns_iter_summ: stats::Summary,
    priv mb_s: uint
}

#[deriving(Clone, Eq)]
pub enum TestResult {
    TrOk,
    TrFailed,
    TrIgnored,
    TrMetrics(MetricMap),
    TrBench(BenchSamples),
}

enum OutputLocation<T> {
    Pretty(term::Terminal<T>),
    Raw(T),
}

struct ConsoleTestState<T> {
    log_out: Option<File>,
    out: OutputLocation<T>,
    use_color: bool,
    total: uint,
    passed: uint,
    failed: uint,
    ignored: uint,
    measured: uint,
    metrics: MetricMap,
    failures: ~[(TestDesc, ~[u8])],
    max_name_len: uint, // number of columns to fill when aligning names
}

impl<T: Writer> ConsoleTestState<T> {
    pub fn new(opts: &TestOpts,
               _: Option<T>) -> io::IoResult<ConsoleTestState<StdWriter>> {
        let log_out = match opts.logfile {
            Some(ref path) => Some(try!(File::create(path))),
            None => None
        };
        let out = match term::Terminal::new(io::stdout()) {
            Err(_) => Raw(io::stdout()),
            Ok(t) => Pretty(t)
        };
        Ok(ConsoleTestState {
            out: out,
            log_out: log_out,
            use_color: use_color(),
            total: 0u,
            passed: 0u,
            failed: 0u,
            ignored: 0u,
            measured: 0u,
            metrics: MetricMap::new(),
            failures: ~[],
            max_name_len: 0u,
        })
    }

    pub fn write_ok(&mut self) -> io::IoResult<()> {
        self.write_pretty("ok", term::color::GREEN)
    }

    pub fn write_failed(&mut self) -> io::IoResult<()> {
        self.write_pretty("FAILED", term::color::RED)
    }

    pub fn write_ignored(&mut self) -> io::IoResult<()> {
        self.write_pretty("ignored", term::color::YELLOW)
    }

    pub fn write_metric(&mut self) -> io::IoResult<()> {
        self.write_pretty("metric", term::color::CYAN)
    }

    pub fn write_bench(&mut self) -> io::IoResult<()> {
        self.write_pretty("bench", term::color::CYAN)
    }

    pub fn write_added(&mut self) -> io::IoResult<()> {
        self.write_pretty("added", term::color::GREEN)
    }

    pub fn write_improved(&mut self) -> io::IoResult<()> {
        self.write_pretty("improved", term::color::GREEN)
    }

    pub fn write_removed(&mut self) -> io::IoResult<()> {
        self.write_pretty("removed", term::color::YELLOW)
    }

    pub fn write_regressed(&mut self) -> io::IoResult<()> {
        self.write_pretty("regressed", term::color::RED)
    }

    pub fn write_pretty(&mut self,
                        word: &str,
                        color: term::color::Color) -> io::IoResult<()> {
        match self.out {
            Pretty(ref mut term) => {
                if self.use_color {
                    try!(term.fg(color));
                }
                try!(term.write(word.as_bytes()));
                if self.use_color {
                    try!(term.reset());
                }
                Ok(())
            }
            Raw(ref mut stdout) => stdout.write(word.as_bytes())
        }
    }

    pub fn write_plain(&mut self, s: &str) -> io::IoResult<()> {
        match self.out {
            Pretty(ref mut term) => term.write(s.as_bytes()),
            Raw(ref mut stdout) => stdout.write(s.as_bytes())
        }
    }

    pub fn write_run_start(&mut self, len: uint) -> io::IoResult<()> {
        self.total = len;
        let noun = if len != 1 { &"tests" } else { &"test" };
        self.write_plain(format!("\nrunning {} {}\n", len, noun))
    }

    pub fn write_test_start(&mut self, test: &TestDesc,
                            align: NamePadding) -> io::IoResult<()> {
        let name = test.padded_name(self.max_name_len, align);
        self.write_plain(format!("test {} ... ", name))
    }

    pub fn write_result(&mut self, result: &TestResult) -> io::IoResult<()> {
        try!(match *result {
            TrOk => self.write_ok(),
            TrFailed => self.write_failed(),
            TrIgnored => self.write_ignored(),
            TrMetrics(ref mm) => {
                try!(self.write_metric());
                self.write_plain(format!(": {}", fmt_metrics(mm)))
            }
            TrBench(ref bs) => {
                try!(self.write_bench());
                self.write_plain(format!(": {}", fmt_bench_samples(bs)))
            }
        });
        self.write_plain("\n")
    }

    pub fn write_log(&mut self, test: &TestDesc,
                     result: &TestResult) -> io::IoResult<()> {
        match self.log_out {
            None => Ok(()),
            Some(ref mut o) => {
                let s = format!("{} {}\n", match *result {
                        TrOk => ~"ok",
                        TrFailed => ~"failed",
                        TrIgnored => ~"ignored",
                        TrMetrics(ref mm) => fmt_metrics(mm),
                        TrBench(ref bs) => fmt_bench_samples(bs)
                    }, test.name.to_str());
                o.write(s.as_bytes())
            }
        }
    }

    pub fn write_failures(&mut self) -> io::IoResult<()> {
        try!(self.write_plain("\nfailures:\n"));
        let mut failures = ~[];
        let mut fail_out  = ~"";
        for &(ref f, ref stdout) in self.failures.iter() {
            failures.push(f.name.to_str());
            if stdout.len() > 0 {
                fail_out.push_str(format!("---- {} stdout ----\n\t",
                                  f.name.to_str()));
                let output = str::from_utf8_lossy(*stdout);
                fail_out.push_str(output.as_slice().replace("\n", "\n\t"));
                fail_out.push_str("\n");
            }
        }
        if fail_out.len() > 0 {
            try!(self.write_plain("\n"));
            try!(self.write_plain(fail_out));
        }

        try!(self.write_plain("\nfailures:\n"));
        failures.sort();
        for name in failures.iter() {
            try!(self.write_plain(format!("    {}\n", name.to_str())));
        }
        Ok(())
    }

    pub fn write_metric_diff(&mut self, diff: &MetricDiff) -> io::IoResult<()> {
        let mut noise = 0;
        let mut improved = 0;
        let mut regressed = 0;
        let mut added = 0;
        let mut removed = 0;

        for (k, v) in diff.iter() {
            match *v {
                LikelyNoise => noise += 1,
                MetricAdded => {
                    added += 1;
                    try!(self.write_added());
                    try!(self.write_plain(format!(": {}\n", *k)));
                }
                MetricRemoved => {
                    removed += 1;
                    try!(self.write_removed());
                    try!(self.write_plain(format!(": {}\n", *k)));
                }
                Improvement(pct) => {
                    improved += 1;
                    try!(self.write_plain(format!(": {}", *k)));
                    try!(self.write_improved());
                    try!(self.write_plain(format!(" by {:.2f}%\n", pct as f64)));
                }
                Regression(pct) => {
                    regressed += 1;
                    try!(self.write_plain(format!(": {}", *k)));
                    try!(self.write_regressed());
                    try!(self.write_plain(format!(" by {:.2f}%\n", pct as f64)));
                }
            }
        }
        try!(self.write_plain(format!("result of ratchet: {} metrics added, \
                                        {} removed, {} improved, {} regressed, \
                                        {} noise\n",
                                       added, removed, improved, regressed,
                                       noise)));
        if regressed == 0 {
            try!(self.write_plain("updated ratchet file\n"));
        } else {
            try!(self.write_plain("left ratchet file untouched\n"));
        }
        Ok(())
    }

    pub fn write_run_finish(&mut self,
                            ratchet_metrics: &Option<Path>,
                            ratchet_pct: Option<f64>) -> io::IoResult<bool> {
        assert!(self.passed + self.failed + self.ignored + self.measured == self.total);

        let ratchet_success = match *ratchet_metrics {
            None => true,
            Some(ref pth) => {
                try!(self.write_plain(format!("\nusing metrics ratcher: {}\n",
                                        pth.display())));
                match ratchet_pct {
                    None => (),
                    Some(pct) =>
                        try!(self.write_plain(format!("with noise-tolerance \
                                                         forced to: {}%\n",
                                                        pct)))
                }
                let (diff, ok) = self.metrics.ratchet(pth, ratchet_pct);
                try!(self.write_metric_diff(&diff));
                ok
            }
        };

        let test_success = self.failed == 0u;
        if !test_success {
            try!(self.write_failures());
        }

        let success = ratchet_success && test_success;

        try!(self.write_plain("\ntest result: "));
        if success {
            // There's no parallelism at this point so it's safe to use color
            try!(self.write_ok());
        } else {
            try!(self.write_failed());
        }
        let s = format!(". {} passed; {} failed; {} ignored; {} measured\n\n",
                        self.passed, self.failed, self.ignored, self.measured);
        try!(self.write_plain(s));
        return Ok(success);
    }
}

pub fn fmt_metrics(mm: &MetricMap) -> ~str {
    let MetricMap(ref mm) = *mm;
    let v : ~[~str] = mm.iter()
        .map(|(k,v)| format!("{}: {} (+/- {})",
                          *k,
                          v.value as f64,
                          v.noise as f64))
        .collect();
    v.connect(", ")
}

pub fn fmt_bench_samples(bs: &BenchSamples) -> ~str {
    if bs.mb_s != 0 {
        format!("{:>9} ns/iter (+/- {}) = {} MB/s",
             bs.ns_iter_summ.median as uint,
             (bs.ns_iter_summ.max - bs.ns_iter_summ.min) as uint,
             bs.mb_s)
    } else {
        format!("{:>9} ns/iter (+/- {})",
             bs.ns_iter_summ.median as uint,
             (bs.ns_iter_summ.max - bs.ns_iter_summ.min) as uint)
    }
}

// A simple console test runner
pub fn run_tests_console(opts: &TestOpts,
                         tests: ~[TestDescAndFn]) -> io::IoResult<bool> {
    fn callback<T: Writer>(event: &TestEvent,
                           st: &mut ConsoleTestState<T>) -> io::IoResult<()> {
        debug!("callback(event={:?})", event);
        match (*event).clone() {
            TeFiltered(ref filtered_tests) => st.write_run_start(filtered_tests.len()),
            TeWait(ref test, padding) => st.write_test_start(test, padding),
            TeResult(test, result, stdout) => {
                try!(st.write_log(&test, &result));
                try!(st.write_result(&result));
                match result {
                    TrOk => st.passed += 1,
                    TrIgnored => st.ignored += 1,
                    TrMetrics(mm) => {
                        let tname = test.name.to_str();
                        let MetricMap(mm) = mm;
                        for (k,v) in mm.iter() {
                            st.metrics.insert_metric(tname + "." + *k,
                                                     v.value, v.noise);
                        }
                        st.measured += 1
                    }
                    TrBench(bs) => {
                        st.metrics.insert_metric(test.name.to_str(),
                                                 bs.ns_iter_summ.median,
                                                 bs.ns_iter_summ.max - bs.ns_iter_summ.min);
                        st.measured += 1
                    }
                    TrFailed => {
                        st.failed += 1;
                        st.failures.push((test, stdout));
                    }
                }
                Ok(())
            }
        }
    }
    let mut st = try!(ConsoleTestState::new(opts, None::<StdWriter>));
    fn len_if_padded(t: &TestDescAndFn) -> uint {
        match t.testfn.padding() {
            PadNone => 0u,
            PadOnLeft | PadOnRight => t.desc.name.to_str().len(),
        }
    }
    match tests.iter().max_by(|t|len_if_padded(*t)) {
        Some(t) => {
            let n = t.desc.name.to_str();
            debug!("Setting max_name_len from: {}", n);
            st.max_name_len = n.len();
        },
        None => {}
    }
    try!(run_tests(opts, tests, |x| callback(&x, &mut st)));
    match opts.save_metrics {
        None => (),
        Some(ref pth) => {
            try!(st.metrics.save(pth));
            try!(st.write_plain(format!("\nmetrics saved to: {}",
                                          pth.display())));
        }
    }
    return st.write_run_finish(&opts.ratchet_metrics, opts.ratchet_noise_percent);
}

#[test]
fn should_sort_failures_before_printing_them() {
    use std::io::MemWriter;
    use std::str;

    let test_a = TestDesc {
        name: StaticTestName("a"),
        ignore: false,
        should_fail: false
    };

    let test_b = TestDesc {
        name: StaticTestName("b"),
        ignore: false,
        should_fail: false
    };

    let mut st = ConsoleTestState {
        log_out: None,
        out: Raw(MemWriter::new()),
        use_color: false,
        total: 0u,
        passed: 0u,
        failed: 0u,
        ignored: 0u,
        measured: 0u,
        max_name_len: 10u,
        metrics: MetricMap::new(),
        failures: ~[(test_b, ~[]), (test_a, ~[])]
    };

    st.write_failures().unwrap();
    let s = match st.out {
        Raw(ref m) => str::from_utf8_lossy(m.get_ref()),
        Pretty(_) => unreachable!()
    };

    let apos = s.as_slice().find_str("a").unwrap();
    let bpos = s.as_slice().find_str("b").unwrap();
    assert!(apos < bpos);
}

fn use_color() -> bool { return get_concurrency() == 1; }

#[deriving(Clone)]
enum TestEvent {
    TeFiltered(~[TestDesc]),
    TeWait(TestDesc, NamePadding),
    TeResult(TestDesc, TestResult, ~[u8] /* stdout */),
}

pub type MonitorMsg = (TestDesc, TestResult, ~[u8] /* stdout */);

fn run_tests(opts: &TestOpts,
             tests: ~[TestDescAndFn],
             callback: |e: TestEvent| -> io::IoResult<()>) -> io::IoResult<()> {
    let filtered_tests = filter_tests(opts, tests);
    let filtered_descs = filtered_tests.map(|t| t.desc.clone());

    try!(callback(TeFiltered(filtered_descs)));

    let (filtered_tests, filtered_benchs_and_metrics) =
        filtered_tests.partition(|e| {
            match e.testfn {
                StaticTestFn(_) | DynTestFn(_) => true,
                _ => false
            }
        });

    // It's tempting to just spawn all the tests at once, but since we have
    // many tests that run in other processes we would be making a big mess.
    let concurrency = get_concurrency();
    debug!("using {} test tasks", concurrency);

    let mut remaining = filtered_tests;
    remaining.reverse();
    let mut pending = 0;

    let (p, ch) = Chan::<MonitorMsg>::new();

    while pending > 0 || !remaining.is_empty() {
        while pending < concurrency && !remaining.is_empty() {
            let test = remaining.pop().unwrap();
            if concurrency == 1 {
                // We are doing one test at a time so we can print the name
                // of the test before we run it. Useful for debugging tests
                // that hang forever.
                try!(callback(TeWait(test.desc.clone(), test.testfn.padding())));
            }
            run_test(!opts.run_tests, test, ch.clone());
            pending += 1;
        }

        let (desc, result, stdout) = p.recv();
        if concurrency != 1 {
            try!(callback(TeWait(desc.clone(), PadNone)));
        }
        try!(callback(TeResult(desc, result, stdout)));
        pending -= 1;
    }

    // All benchmarks run at the end, in serial.
    // (this includes metric fns)
    for b in filtered_benchs_and_metrics.move_iter() {
        try!(callback(TeWait(b.desc.clone(), b.testfn.padding())));
        run_test(!opts.run_benchmarks, b, ch.clone());
        let (test, result, stdout) = p.recv();
        try!(callback(TeResult(test, result, stdout)));
    }
    Ok(())
}

fn get_concurrency() -> uint {
    use std::rt;
    match os::getenv("RUST_TEST_TASKS") {
        Some(s) => {
            let opt_n: Option<uint> = FromStr::from_str(s);
            match opt_n {
                Some(n) if n > 0 => n,
                _ => fail!("RUST_TEST_TASKS is `{}`, should be a positive integer.", s)
            }
        }
        None => {
            rt::default_sched_threads()
        }
    }
}

pub fn filter_tests(
    opts: &TestOpts,
    tests: ~[TestDescAndFn]) -> ~[TestDescAndFn]
{
    let mut filtered = tests;

    // Remove tests that don't match the test filter
    filtered = if opts.filter.is_none() {
        filtered
    } else {
        let filter_str = match opts.filter {
          Some(ref f) => (*f).clone(),
          None => ~""
        };

        fn filter_fn(test: TestDescAndFn, filter_str: &str) ->
            Option<TestDescAndFn> {
            if test.desc.name.to_str().contains(filter_str) {
                return Some(test);
            } else {
                return None;
            }
        }

        filtered.move_iter().filter_map(|x| filter_fn(x, filter_str)).collect()
    };

    // Maybe pull out the ignored test and unignore them
    filtered = if !opts.run_ignored {
        filtered
    } else {
        fn filter(test: TestDescAndFn) -> Option<TestDescAndFn> {
            if test.desc.ignore {
                let TestDescAndFn {desc, testfn} = test;
                Some(TestDescAndFn {
                    desc: TestDesc {ignore: false, ..desc},
                    testfn: testfn
                })
            } else {
                None
            }
        };
        filtered.move_iter().filter_map(|x| filter(x)).collect()
    };

    // Sort the tests alphabetically
    filtered.sort_by(|t1, t2| t1.desc.name.to_str().cmp(&t2.desc.name.to_str()));

    // Shard the remaining tests, if sharding requested.
    match opts.test_shard {
        None => filtered,
        Some((a,b)) =>
            filtered.move_iter().enumerate()
            .filter(|&(i,_)| i % b == a)
            .map(|(_,t)| t)
            .to_owned_vec()
    }
}

pub fn run_test(force_ignore: bool,
                test: TestDescAndFn,
                monitor_ch: Chan<MonitorMsg>) {

    let TestDescAndFn {desc, testfn} = test;

    if force_ignore || desc.ignore {
        monitor_ch.send((desc, TrIgnored, ~[]));
        return;
    }

    fn run_test_inner(desc: TestDesc,
                      monitor_ch: Chan<MonitorMsg>,
                      testfn: proc()) {
        spawn(proc() {
            let (p, c) = Chan::new();
            let mut reader = PortReader::new(p);
            let stdout = ChanWriter::new(c.clone());
            let stderr = ChanWriter::new(c);
            let mut task = task::task().named(match desc.name {
                DynTestName(ref name) => name.clone().into_maybe_owned(),
                StaticTestName(name) => name.into_maybe_owned(),
            });
            task.opts.stdout = Some(~stdout as ~Writer);
            task.opts.stderr = Some(~stderr as ~Writer);
            let result_future = task.future_result();
            task.spawn(testfn);

            let stdout = reader.read_to_end().unwrap();
            let task_result = result_future.recv();
            let test_result = calc_result(&desc, task_result.is_ok());
            monitor_ch.send((desc.clone(), test_result, stdout));
        })
    }

    match testfn {
        DynBenchFn(bencher) => {
            let bs = ::bench::benchmark(|harness| bencher.run(harness));
            monitor_ch.send((desc, TrBench(bs), ~[]));
            return;
        }
        StaticBenchFn(benchfn) => {
            let bs = ::bench::benchmark(|harness| benchfn(harness));
            monitor_ch.send((desc, TrBench(bs), ~[]));
            return;
        }
        DynMetricFn(f) => {
            let mut mm = MetricMap::new();
            f(&mut mm);
            monitor_ch.send((desc, TrMetrics(mm), ~[]));
            return;
        }
        StaticMetricFn(f) => {
            let mut mm = MetricMap::new();
            f(&mut mm);
            monitor_ch.send((desc, TrMetrics(mm), ~[]));
            return;
        }
        DynTestFn(f) => run_test_inner(desc, monitor_ch, f),
        StaticTestFn(f) => run_test_inner(desc, monitor_ch, proc() f())
    }
}

fn calc_result(desc: &TestDesc, task_succeeded: bool) -> TestResult {
    if task_succeeded {
        if desc.should_fail { TrFailed }
        else { TrOk }
    } else {
        if desc.should_fail { TrOk }
        else { TrFailed }
    }
}


impl ToJson for Metric {
    fn to_json(&self) -> json::Json {
        let mut map = ~TreeMap::new();
        map.insert(~"value", json::Number(self.value));
        map.insert(~"noise", json::Number(self.noise));
        json::Object(map)
    }
}

impl MetricMap {

    pub fn new() -> MetricMap {
        MetricMap(TreeMap::new())
    }

    /// Load MetricDiff from a file.
    ///
    /// # Failure
    ///
    /// This function will fail if the path does not exist or the path does not
    /// contain a valid metric map.
    pub fn load(p: &Path) -> MetricMap {
        assert!(p.exists());
        let mut f = File::open(p).unwrap();
        let value = json::from_reader(&mut f as &mut io::Reader).unwrap();
        let mut decoder = json::Decoder::new(value);
        MetricMap(Decodable::decode(&mut decoder))
    }

    /// Write MetricDiff to a file.
    pub fn save(&self, p: &Path) -> io::IoResult<()> {
        let mut file = try!(File::create(p));
        let MetricMap(ref map) = *self;
        map.to_json().to_pretty_writer(&mut file)
    }

    /// Compare against another MetricMap. Optionally compare all
    /// measurements in the maps using the provided `noise_pct` as a
    /// percentage of each value to consider noise. If `None`, each
    /// measurement's noise threshold is independently chosen as the
    /// maximum of that measurement's recorded noise quantity in either
    /// map.
    pub fn compare_to_old(&self, old: &MetricMap,
                          noise_pct: Option<f64>) -> MetricDiff {
        let mut diff : MetricDiff = TreeMap::new();
        let MetricMap(ref selfmap) = *self;
        let MetricMap(ref old) = *old;
        for (k, vold) in old.iter() {
            let r = match selfmap.find(k) {
                None => MetricRemoved,
                Some(v) => {
                    let delta = (v.value - vold.value);
                    let noise = match noise_pct {
                        None => f64::max(vold.noise.abs(), v.noise.abs()),
                        Some(pct) => vold.value * pct / 100.0
                    };
                    if delta.abs() <= noise {
                        LikelyNoise
                    } else {
                        let pct = delta.abs() / cmp::max(vold.value, f64::EPSILON) * 100.0;
                        if vold.noise < 0.0 {
                            // When 'noise' is negative, it means we want
                            // to see deltas that go up over time, and can
                            // only tolerate slight negative movement.
                            if delta < 0.0 {
                                Regression(pct)
                            } else {
                                Improvement(pct)
                            }
                        } else {
                            // When 'noise' is positive, it means we want
                            // to see deltas that go down over time, and
                            // can only tolerate slight positive movements.
                            if delta < 0.0 {
                                Improvement(pct)
                            } else {
                                Regression(pct)
                            }
                        }
                    }
                }
            };
            diff.insert((*k).clone(), r);
        }
        let MetricMap(ref map) = *self;
        for (k, _) in map.iter() {
            if !diff.contains_key(k) {
                diff.insert((*k).clone(), MetricAdded);
            }
        }
        diff
    }

    /// Insert a named `value` (+/- `noise`) metric into the map. The value
    /// must be non-negative. The `noise` indicates the uncertainty of the
    /// metric, which doubles as the "noise range" of acceptable
    /// pairwise-regressions on this named value, when comparing from one
    /// metric to the next using `compare_to_old`.
    ///
    /// If `noise` is positive, then it means this metric is of a value
    /// you want to see grow smaller, so a change larger than `noise` in the
    /// positive direction represents a regression.
    ///
    /// If `noise` is negative, then it means this metric is of a value
    /// you want to see grow larger, so a change larger than `noise` in the
    /// negative direction represents a regression.
    pub fn insert_metric(&mut self, name: &str, value: f64, noise: f64) {
        let m = Metric {
            value: value,
            noise: noise
        };
        let MetricMap(ref mut map) = *self;
        map.insert(name.to_owned(), m);
    }

    /// Attempt to "ratchet" an external metric file. This involves loading
    /// metrics from a metric file (if it exists), comparing against
    /// the metrics in `self` using `compare_to_old`, and rewriting the
    /// file to contain the metrics in `self` if none of the
    /// `MetricChange`s are `Regression`. Returns the diff as well
    /// as a boolean indicating whether the ratchet succeeded.
    pub fn ratchet(&self, p: &Path, pct: Option<f64>) -> (MetricDiff, bool) {
        let old = if p.exists() {
            MetricMap::load(p)
        } else {
            MetricMap::new()
        };

        let diff : MetricDiff = self.compare_to_old(&old, pct);
        let ok = diff.iter().all(|(_, v)| {
            match *v {
                Regression(_) => false,
                _ => true
            }
        });

        if ok {
            debug!("rewriting file '{:?}' with updated metrics", p);
            self.save(p).unwrap();
        }
        return (diff, ok)
    }
}


// Benchmarking

/// A function that is opaque to the optimizer, to allow benchmarks to
/// pretend to use outputs to assist in avoiding dead-code
/// elimination.
///
/// This function is a no-op, and does not even read from `dummy`.
pub fn black_box<T>(dummy: T) {
    // we need to "use" the argument in some way LLVM can't
    // introspect.
    unsafe {asm!("" : : "r"(&dummy))}
}


impl BenchHarness {
    /// Callback for benchmark functions to run in their body.
    pub fn iter<T>(&mut self, inner: || -> T) {
        self.ns_start = precise_time_ns();
        let k = self.iterations;
        for _ in range(0u64, k) {
            black_box(inner());
        }
        self.ns_end = precise_time_ns();
    }

    pub fn ns_elapsed(&mut self) -> u64 {
        if self.ns_start == 0 || self.ns_end == 0 {
            0
        } else {
            self.ns_end - self.ns_start
        }
    }

    pub fn ns_per_iter(&mut self) -> u64 {
        if self.iterations == 0 {
            0
        } else {
            self.ns_elapsed() / cmp::max(self.iterations, 1)
        }
    }

    pub fn bench_n(&mut self, n: u64, f: |&mut BenchHarness|) {
        self.iterations = n;
        debug!("running benchmark for {} iterations",
               n as uint);
        f(self);
    }

    // This is a more statistics-driven benchmark algorithm
    pub fn auto_bench(&mut self, f: |&mut BenchHarness|) -> stats::Summary {

        // Initial bench run to get ballpark figure.
        let mut n = 1_u64;
        self.bench_n(n, |x| f(x));

        // Try to estimate iter count for 1ms falling back to 1m
        // iterations if first run took < 1ns.
        if self.ns_per_iter() == 0 {
            n = 1_000_000;
        } else {
            n = 1_000_000 / cmp::max(self.ns_per_iter(), 1);
        }
        // if the first run took more than 1ms we don't want to just
        // be left doing 0 iterations on every loop. The unfortunate
        // side effect of not being able to do as many runs is
        // automatically handled by the statistical analysis below
        // (i.e. larger error bars).
        if n == 0 { n = 1; }

        debug!("Initial run took {} ns, iter count that takes 1ms estimated as {}",
               self.ns_per_iter(), n);

        let mut total_run = 0;
        let samples : &mut [f64] = [0.0_f64, ..50];
        loop {
            let loop_start = precise_time_ns();

            for p in samples.mut_iter() {
                self.bench_n(n, |x| f(x));
                *p = self.ns_per_iter() as f64;
            };

            stats::winsorize(samples, 5.0);
            let summ = stats::Summary::new(samples);

            for p in samples.mut_iter() {
                self.bench_n(5 * n, |x| f(x));
                *p = self.ns_per_iter() as f64;
            };

            stats::winsorize(samples, 5.0);
            let summ5 = stats::Summary::new(samples);

            debug!("{} samples, median {}, MAD={}, MADP={}",
                   samples.len(),
                   summ.median as f64,
                   summ.median_abs_dev as f64,
                   summ.median_abs_dev_pct as f64);

            let now = precise_time_ns();
            let loop_run = now - loop_start;

            // If we've run for 100ms and seem to have converged to a
            // stable median.
            if loop_run > 100_000_000 &&
                summ.median_abs_dev_pct < 1.0 &&
                summ.median - summ5.median < summ5.median_abs_dev {
                return summ5;
            }

            total_run += loop_run;
            // Longest we ever run for is 3s.
            if total_run > 3_000_000_000 {
                return summ5;
            }

            n *= 2;
        }
    }
}

pub mod bench {
    use std::cmp;
    use super::{BenchHarness, BenchSamples};

    pub fn benchmark(f: |&mut BenchHarness|) -> BenchSamples {
        let mut bs = BenchHarness {
            iterations: 0,
            ns_start: 0,
            ns_end: 0,
            bytes: 0
        };

        let ns_iter_summ = bs.auto_bench(f);

        let ns_iter = cmp::max(ns_iter_summ.median as u64, 1);
        let iter_s = 1_000_000_000 / ns_iter;
        let mb_s = (bs.bytes * iter_s) / 1_000_000;

        BenchSamples {
            ns_iter_summ: ns_iter_summ,
            mb_s: mb_s as uint
        }
    }
}

#[cfg(test)]
mod tests {
    use test::{TrFailed, TrIgnored, TrOk, filter_tests, parse_opts,
               TestDesc, TestDescAndFn, TestOpts, run_test,
               Metric, MetricMap, MetricAdded, MetricRemoved,
               Improvement, Regression, LikelyNoise,
               StaticTestName, DynTestName, DynTestFn};
    use extra::tempfile::TempDir;

    #[test]
    pub fn do_not_run_ignored_tests() {
        fn f() { fail!(); }
        let desc = TestDescAndFn {
            desc: TestDesc {
                name: StaticTestName("whatever"),
                ignore: true,
                should_fail: false
            },
            testfn: DynTestFn(proc() f()),
        };
        let (p, ch) = Chan::new();
        run_test(false, desc, ch);
        let (_, res, _) = p.recv();
        assert!(res != TrOk);
    }

    #[test]
    pub fn ignored_tests_result_in_ignored() {
        fn f() { }
        let desc = TestDescAndFn {
            desc: TestDesc {
                name: StaticTestName("whatever"),
                ignore: true,
                should_fail: false
            },
            testfn: DynTestFn(proc() f()),
        };
        let (p, ch) = Chan::new();
        run_test(false, desc, ch);
        let (_, res, _) = p.recv();
        assert_eq!(res, TrIgnored);
    }

    #[test]
    fn test_should_fail() {
        fn f() { fail!(); }
        let desc = TestDescAndFn {
            desc: TestDesc {
                name: StaticTestName("whatever"),
                ignore: false,
                should_fail: true
            },
            testfn: DynTestFn(proc() f()),
        };
        let (p, ch) = Chan::new();
        run_test(false, desc, ch);
        let (_, res, _) = p.recv();
        assert_eq!(res, TrOk);
    }

    #[test]
    fn test_should_fail_but_succeeds() {
        fn f() { }
        let desc = TestDescAndFn {
            desc: TestDesc {
                name: StaticTestName("whatever"),
                ignore: false,
                should_fail: true
            },
            testfn: DynTestFn(proc() f()),
        };
        let (p, ch) = Chan::new();
        run_test(false, desc, ch);
        let (_, res, _) = p.recv();
        assert_eq!(res, TrFailed);
    }

    #[test]
    fn first_free_arg_should_be_a_filter() {
        let args = ~[~"progname", ~"filter"];
        let opts = match parse_opts(args) {
            Some(Ok(o)) => o,
            _ => fail!("Malformed arg in first_free_arg_should_be_a_filter")
        };
        assert!("filter" == opts.filter.clone().unwrap());
    }

    #[test]
    fn parse_ignored_flag() {
        let args = ~[~"progname", ~"filter", ~"--ignored"];
        let opts = match parse_opts(args) {
            Some(Ok(o)) => o,
            _ => fail!("Malformed arg in parse_ignored_flag")
        };
        assert!((opts.run_ignored));
    }

    #[test]
    pub fn filter_for_ignored_option() {
        // When we run ignored tests the test filter should filter out all the
        // unignored tests and flip the ignore flag on the rest to false

        let opts = TestOpts {
            filter: None,
            run_ignored: true,
            logfile: None,
            run_tests: true,
            run_benchmarks: false,
            ratchet_noise_percent: None,
            ratchet_metrics: None,
            save_metrics: None,
            test_shard: None
        };

        let tests = ~[
            TestDescAndFn {
                desc: TestDesc {
                    name: StaticTestName("1"),
                    ignore: true,
                    should_fail: false,
                },
                testfn: DynTestFn(proc() {}),
            },
            TestDescAndFn {
                desc: TestDesc {
                    name: StaticTestName("2"),
                    ignore: false,
                    should_fail: false
                },
                testfn: DynTestFn(proc() {}),
            },
        ];
        let filtered = filter_tests(&opts, tests);

        assert_eq!(filtered.len(), 1);
        assert_eq!(filtered[0].desc.name.to_str(), ~"1");
        assert!(filtered[0].desc.ignore == false);
    }

    #[test]
    pub fn sort_tests() {
        let opts = TestOpts {
            filter: None,
            run_ignored: false,
            logfile: None,
            run_tests: true,
            run_benchmarks: false,
            ratchet_noise_percent: None,
            ratchet_metrics: None,
            save_metrics: None,
            test_shard: None
        };

        let names =
            ~[~"sha1::test", ~"int::test_to_str", ~"int::test_pow",
             ~"test::do_not_run_ignored_tests",
             ~"test::ignored_tests_result_in_ignored",
             ~"test::first_free_arg_should_be_a_filter",
             ~"test::parse_ignored_flag", ~"test::filter_for_ignored_option",
             ~"test::sort_tests"];
        let tests =
        {
            fn testfn() { }
            let mut tests = ~[];
            for name in names.iter() {
                let test = TestDescAndFn {
                    desc: TestDesc {
                        name: DynTestName((*name).clone()),
                        ignore: false,
                        should_fail: false
                    },
                    testfn: DynTestFn(testfn),
                };
                tests.push(test);
            }
            tests
        };
        let filtered = filter_tests(&opts, tests);

        let expected =
            ~[~"int::test_pow", ~"int::test_to_str", ~"sha1::test",
              ~"test::do_not_run_ignored_tests",
              ~"test::filter_for_ignored_option",
              ~"test::first_free_arg_should_be_a_filter",
              ~"test::ignored_tests_result_in_ignored",
              ~"test::parse_ignored_flag",
              ~"test::sort_tests"];

        for (a, b) in expected.iter().zip(filtered.iter()) {
            assert!(*a == b.desc.name.to_str());
        }
    }

    #[test]
    pub fn test_metricmap_compare() {
        let mut m1 = MetricMap::new();
        let mut m2 = MetricMap::new();
        m1.insert_metric("in-both-noise", 1000.0, 200.0);
        m2.insert_metric("in-both-noise", 1100.0, 200.0);

        m1.insert_metric("in-first-noise", 1000.0, 2.0);
        m2.insert_metric("in-second-noise", 1000.0, 2.0);

        m1.insert_metric("in-both-want-downwards-but-regressed", 1000.0, 10.0);
        m2.insert_metric("in-both-want-downwards-but-regressed", 2000.0, 10.0);

        m1.insert_metric("in-both-want-downwards-and-improved", 2000.0, 10.0);
        m2.insert_metric("in-both-want-downwards-and-improved", 1000.0, 10.0);

        m1.insert_metric("in-both-want-upwards-but-regressed", 2000.0, -10.0);
        m2.insert_metric("in-both-want-upwards-but-regressed", 1000.0, -10.0);

        m1.insert_metric("in-both-want-upwards-and-improved", 1000.0, -10.0);
        m2.insert_metric("in-both-want-upwards-and-improved", 2000.0, -10.0);

        let diff1 = m2.compare_to_old(&m1, None);

        assert_eq!(*(diff1.find(&~"in-both-noise").unwrap()), LikelyNoise);
        assert_eq!(*(diff1.find(&~"in-first-noise").unwrap()), MetricRemoved);
        assert_eq!(*(diff1.find(&~"in-second-noise").unwrap()), MetricAdded);
        assert_eq!(*(diff1.find(&~"in-both-want-downwards-but-regressed").unwrap()),
                   Regression(100.0));
        assert_eq!(*(diff1.find(&~"in-both-want-downwards-and-improved").unwrap()),
                   Improvement(50.0));
        assert_eq!(*(diff1.find(&~"in-both-want-upwards-but-regressed").unwrap()),
                   Regression(50.0));
        assert_eq!(*(diff1.find(&~"in-both-want-upwards-and-improved").unwrap()),
                   Improvement(100.0));
        assert_eq!(diff1.len(), 7);

        let diff2 = m2.compare_to_old(&m1, Some(200.0));

        assert_eq!(*(diff2.find(&~"in-both-noise").unwrap()), LikelyNoise);
        assert_eq!(*(diff2.find(&~"in-first-noise").unwrap()), MetricRemoved);
        assert_eq!(*(diff2.find(&~"in-second-noise").unwrap()), MetricAdded);
        assert_eq!(*(diff2.find(&~"in-both-want-downwards-but-regressed").unwrap()), LikelyNoise);
        assert_eq!(*(diff2.find(&~"in-both-want-downwards-and-improved").unwrap()), LikelyNoise);
        assert_eq!(*(diff2.find(&~"in-both-want-upwards-but-regressed").unwrap()), LikelyNoise);
        assert_eq!(*(diff2.find(&~"in-both-want-upwards-and-improved").unwrap()), LikelyNoise);
        assert_eq!(diff2.len(), 7);
    }

    #[test]
    pub fn ratchet_test() {

        let dpth = TempDir::new("test-ratchet").expect("missing test for ratchet");
        let pth = dpth.path().join("ratchet.json");

        let mut m1 = MetricMap::new();
        m1.insert_metric("runtime", 1000.0, 2.0);
        m1.insert_metric("throughput", 50.0, 2.0);

        let mut m2 = MetricMap::new();
        m2.insert_metric("runtime", 1100.0, 2.0);
        m2.insert_metric("throughput", 50.0, 2.0);

        m1.save(&pth).unwrap();

        // Ask for a ratchet that should fail to advance.
        let (diff1, ok1) = m2.ratchet(&pth, None);
        assert_eq!(ok1, false);
        assert_eq!(diff1.len(), 2);
        assert_eq!(*(diff1.find(&~"runtime").unwrap()), Regression(10.0));
        assert_eq!(*(diff1.find(&~"throughput").unwrap()), LikelyNoise);

        // Check that it was not rewritten.
        let m3 = MetricMap::load(&pth);
        let MetricMap(m3) = m3;
        assert_eq!(m3.len(), 2);
        assert_eq!(*(m3.find(&~"runtime").unwrap()), Metric::new(1000.0, 2.0));
        assert_eq!(*(m3.find(&~"throughput").unwrap()), Metric::new(50.0, 2.0));

        // Ask for a ratchet with an explicit noise-percentage override,
        // that should advance.
        let (diff2, ok2) = m2.ratchet(&pth, Some(10.0));
        assert_eq!(ok2, true);
        assert_eq!(diff2.len(), 2);
        assert_eq!(*(diff2.find(&~"runtime").unwrap()), LikelyNoise);
        assert_eq!(*(diff2.find(&~"throughput").unwrap()), LikelyNoise);

        // Check that it was rewritten.
        let m4 = MetricMap::load(&pth);
        let MetricMap(m4) = m4;
        assert_eq!(m4.len(), 2);
        assert_eq!(*(m4.find(&~"runtime").unwrap()), Metric::new(1100.0, 2.0));
        assert_eq!(*(m4.find(&~"throughput").unwrap()), Metric::new(50.0, 2.0));
    }
}