Add method_call_assertions and use them instead of Mocha

Six Mocha calls prove quite resistant to Minitestification. For example,
if we replace

```
  ActiveRecord::Associations::HasManyAssociation
    .any_instance
    .expects(:reader)
    .never
```

with `assert_not_called`, Minitest wisely raises

```
NameError: undefined method `reader' for class `ActiveRecord::Associations::HasManyAssociation'
```

as `:reader` comes from a deeply embedded abstract class,
`ActiveRecord::Associations::CollectionAssociation`.

This patch tackles this difficulty by adding
`ActiveSupport::Testing::MethodCallAsserts#assert_called_on_instance_of`
which injects a stubbed method into `klass`, and verifies the number of
times it is called, similar to `assert_called`. It also adds  a convenience
method, `assert_not_called_on_instance_of`, mirroring
`assert_not_called`.

It uses the new method_call_assertions to replace the remaining Mocha
calls in `ActiveRecord` tests.

[utilum + bogdanvlviv + kspath]

activerecord/test/cases/associations/eager_test.rb

@@ -1571,8 +1571,9 @@ def test_preloading_has_many_through_with_custom_scope
 
   # CollectionProxy#reader is expensive, so the preloader avoids calling it.
   test "preloading has_many_through association avoids calling association.reader" do
-    ActiveRecord::Associations::HasManyAssociation.any_instance.expects(:reader).never
-    Author.preload(:readonly_comments).first!
+    assert_not_called_on_instance_of(ActiveRecord::Associations::HasManyAssociation, :reader) do
+      Author.preload(:readonly_comments).first!
+    end
   end
 
   test "preloading through a polymorphic association doesn't require the association to exist" do

activerecord/test/cases/associations/has_many_associations_test.rb

@@ -2134,21 +2134,29 @@ def test_creating_using_primary_key
   end
 
   def test_defining_has_many_association_with_delete_all_dependency_lazily_evaluates_target_class
-    ActiveRecord::Reflection::AssociationReflection.any_instance.expects(:class_name).never
-    class_eval(<<-EOF, __FILE__, __LINE__ + 1)
-      class DeleteAllModel < ActiveRecord::Base
-        has_many :nonentities, :dependent => :delete_all
-      end
-    EOF
+    assert_not_called_on_instance_of(
+      ActiveRecord::Reflection::AssociationReflection,
+      :class_name,
+    ) do
+      class_eval(<<-EOF, __FILE__, __LINE__ + 1)
+        class DeleteAllModel < ActiveRecord::Base
+          has_many :nonentities, :dependent => :delete_all
+        end
+      EOF
+    end
   end
 
   def test_defining_has_many_association_with_nullify_dependency_lazily_evaluates_target_class
-    ActiveRecord::Reflection::AssociationReflection.any_instance.expects(:class_name).never
-    class_eval(<<-EOF, __FILE__, __LINE__ + 1)
-      class NullifyModel < ActiveRecord::Base
-        has_many :nonentities, :dependent => :nullify
-      end
-    EOF
+    assert_not_called_on_instance_of(
+      ActiveRecord::Reflection::AssociationReflection,
+      :class_name,
+    ) do
+      class_eval(<<-EOF, __FILE__, __LINE__ + 1)
+        class NullifyModel < ActiveRecord::Base
+          has_many :nonentities, :dependent => :nullify
+        end
+      EOF
+    end
   end
 
   def test_attributes_are_being_set_when_initialized_from_has_many_association_with_where_clause

activerecord/test/cases/helper.rb

@@ -183,5 +183,3 @@ def in_time_zone(zone)
       ActiveRecord::Base.time_zone_aware_attributes = old_tz
     end
 end
-
-require "mocha/minitest" # FIXME: stop using mocha

activerecord/test/cases/tasks/database_tasks_test.rb

@@ -46,35 +46,46 @@ def with_stubbed_new
 
   class DatabaseTasksUtilsTask < ActiveRecord::TestCase
     def test_raises_an_error_when_called_with_protected_environment
-      ActiveRecord::MigrationContext.any_instance.stubs(:current_version).returns(1)
-
       protected_environments = ActiveRecord::Base.protected_environments
       current_env            = ActiveRecord::Base.connection.migration_context.current_environment
-      assert_not_includes protected_environments, current_env
-      # Assert no error
-      ActiveRecord::Tasks::DatabaseTasks.check_protected_environments!
-
-      ActiveRecord::Base.protected_environments = [current_env]
 
-      assert_raise(ActiveRecord::ProtectedEnvironmentError) do
+      assert_called_on_instance_of(
+        ActiveRecord::MigrationContext,
+        :current_version,
+        times: 6,
+        returns: 1
+      ) do
+        assert_not_includes protected_environments, current_env
+        # Assert no error
         ActiveRecord::Tasks::DatabaseTasks.check_protected_environments!
+
+        ActiveRecord::Base.protected_environments = [current_env]
+
+        assert_raise(ActiveRecord::ProtectedEnvironmentError) do
+          ActiveRecord::Tasks::DatabaseTasks.check_protected_environments!
+        end
       end
     ensure
       ActiveRecord::Base.protected_environments = protected_environments
     end
 
     def test_raises_an_error_when_called_with_protected_environment_which_name_is_a_symbol
-      ActiveRecord::MigrationContext.any_instance.stubs(:current_version).returns(1)
-
       protected_environments = ActiveRecord::Base.protected_environments
       current_env            = ActiveRecord::Base.connection.migration_context.current_environment
-      assert_not_includes protected_environments, current_env
-      # Assert no error
-      ActiveRecord::Tasks::DatabaseTasks.check_protected_environments!
-
-      ActiveRecord::Base.protected_environments = [current_env.to_sym]
-      assert_raise(ActiveRecord::ProtectedEnvironmentError) do
+      assert_called_on_instance_of(
+        ActiveRecord::MigrationContext,
+        :current_version,
+        times: 6,
+        returns: 1
+      ) do
+        assert_not_includes protected_environments, current_env
+        # Assert no error
         ActiveRecord::Tasks::DatabaseTasks.check_protected_environments!
+
+        ActiveRecord::Base.protected_environments = [current_env.to_sym]
+        assert_raise(ActiveRecord::ProtectedEnvironmentError) do
+          ActiveRecord::Tasks::DatabaseTasks.check_protected_environments!
+        end
       end
     ensure
       ActiveRecord::Base.protected_environments = protected_environments
@@ -82,10 +93,14 @@ def test_raises_an_error_when_called_with_protected_environment_which_name_is_a_
 
     def test_raises_an_error_if_no_migrations_have_been_made
       ActiveRecord::InternalMetadata.stub(:table_exists?, false) do
-        ActiveRecord::MigrationContext.any_instance.stubs(:current_version).returns(1)
-
-        assert_raise(ActiveRecord::NoEnvironmentInSchemaError) do
-          ActiveRecord::Tasks::DatabaseTasks.check_protected_environments!
+        assert_called_on_instance_of(
+          ActiveRecord::MigrationContext,
+          :current_version,
+          returns: 1
+        ) do
+          assert_raise(ActiveRecord::NoEnvironmentInSchemaError) do
+            ActiveRecord::Tasks::DatabaseTasks.check_protected_environments!
+          end
         end
       end
     end

activesupport/lib/active_support/testing/method_call_assertions.rb

@@ -35,6 +35,35 @@ def assert_not_called(object, method_name, message = nil, &block)
           assert_called(object, method_name, message, times: 0, &block)
         end
 
+        # TODO: No need to resort to #send once support for Ruby 2.4 is
+        # dropped.
+        def assert_called_on_instance_of(klass, method_name, message = nil, times: 1, returns: nil)
+          times_called = 0
+          klass.send(:define_method, "stubbed_#{method_name}") do |*|
+            times_called += 1
+
+            returns
+          end
+
+          klass.send(:alias_method, "original_#{method_name}", method_name)
+          klass.send(:alias_method, method_name, "stubbed_#{method_name}")
+
+          yield
+
+          error = "Expected #{method_name} to be called #{times} times, but was called #{times_called} times"
+          error = "#{message}.\n#{error}" if message
+
+          assert_equal times, times_called, error
+        ensure
+          klass.send(:alias_method, method_name, "original_#{method_name}")
+          klass.send(:undef_method, "original_#{method_name}")
+          klass.send(:undef_method, "stubbed_#{method_name}")
+        end
+
+        def assert_not_called_on_instance_of(klass, method_name, message = nil, &block)
+          assert_called_on_instance_of(klass, method_name, message, times: 0, &block)
+        end
+
         def stub_any_instance(klass, instance: klass.new)
           klass.stub(:new, instance) { yield instance }
         end

activesupport/test/testing/method_call_assertions_test.rb

@@ -91,6 +91,65 @@ def test_assert_called_with_multiple_expected_arguments
     end
   end
 
+  def test_assert_called_on_instance_of_with_defaults_to_expect_once
+    assert_called_on_instance_of Level, :increment do
+      @object.increment
+    end
+  end
+
+  def test_assert_called_on_instance_of_more_than_once
+    assert_called_on_instance_of(Level, :increment, times: 2) do
+      @object.increment
+      @object.increment
+    end
+  end
+
+  def test_assert_called_on_instance_of_with_arguments
+    assert_called_on_instance_of(Level, :<<) do
+      @object << 2
+    end
+  end
+
+  def test_assert_called_on_instance_of_returns
+    assert_called_on_instance_of(Level, :increment, returns: 10) do
+      assert_equal 10, @object.increment
+    end
+
+    assert_equal 1, @object.increment
+  end
+
+  def test_assert_called_on_instance_of_failure
+    error = assert_raises(Minitest::Assertion) do
+      assert_called_on_instance_of(Level, :increment) do
+        # Call nothing...
+      end
+    end
+
+    assert_equal "Expected increment to be called 1 times, but was called 0 times.\nExpected: 1\n  Actual: 0", error.message
+  end
+
+  def test_assert_called_on_instance_of_with_message
+    error = assert_raises(Minitest::Assertion) do
+      assert_called_on_instance_of(Level, :increment, "dang it") do
+        # Call nothing...
+      end
+    end
+
+    assert_match(/dang it.\nExpected increment/, error.message)
+  end
+
+  def test_assert_called_on_instance_of_nesting
+    assert_called_on_instance_of(Level, :increment, times: 3) do
+      assert_called_on_instance_of(Level, :decrement, times: 2) do
+        @object.increment
+        @object.decrement
+        @object.increment
+        @object.decrement
+        @object.increment
+      end
+    end
+  end
+
   def test_assert_not_called
     assert_not_called(@object, :decrement) do
       @object.increment
@@ -107,6 +166,30 @@ def test_assert_not_called_failure
     assert_equal "Expected increment to be called 0 times, but was called 1 times.\nExpected: 0\n  Actual: 1", error.message
   end
 
+  def test_assert_not_called_on_instance_of
+    assert_not_called_on_instance_of(Level, :decrement) do
+      @object.increment
+    end
+  end
+
+  def test_assert_not_called_on_instance_of_failure
+    error = assert_raises(Minitest::Assertion) do
+      assert_not_called_on_instance_of(Level, :increment) do
+        @object.increment
+      end
+    end
+
+    assert_equal "Expected increment to be called 0 times, but was called 1 times.\nExpected: 0\n  Actual: 1", error.message
+  end
+
+  def test_assert_not_called_on_instance_of_nesting
+    assert_not_called_on_instance_of(Level, :increment) do
+      assert_not_called_on_instance_of(Level, :decrement) do
+        # Call nothing...
+      end
+    end
+  end
+
   def test_stub_any_instance
     stub_any_instance(Level) do |instance|
       assert_equal instance, Level.new