Support for deep `Map` equality with `asserts#equal` (#3236)

std/testing/asserts.ts

@@ -81,6 +81,19 @@ export function equal(c: unknown, d: unknown): boolean {
       }
       return true;
     }
+    if (a && b && a instanceof Map && b instanceof Map) {
+      if (a.size !== b.size) {
+        return false;
+      }
+
+      for (const [key, value] of a) {
+        if (!compare(value, b.get(key))) {
+          return false;
+        }
+      }
+
+      return true;
+    }
     // Have to render RegExp & Date for string comparison
     // unless it's mistreated as object
     if (

std/testing/asserts_test.ts

@@ -47,6 +47,42 @@ test(function testingEqual(): void {
   assert(!equal(new Set([1, 2]), new Set([3, 2, 1])));
   assert(!equal(new Set([1, 2, 3]), new Set([4, 5, 6])));
   assert(equal(new Set("denosaurus"), new Set("denosaurussss")));
+  assert(equal(new Map(), new Map()));
+  assert(
+    equal(
+      new Map([["foo", "bar"], ["baz", "baz"]]),
+      new Map([["foo", "bar"], ["baz", "baz"]])
+    )
+  );
+  assert(
+    equal(
+      new Map([["foo", new Map([["bar", "baz"]])]]),
+      new Map([["foo", new Map([["bar", "baz"]])]])
+    )
+  );
+  assert(
+    equal(
+      new Map([["foo", { bar: "baz" }]]),
+      new Map([["foo", { bar: "baz" }]])
+    )
+  );
+  assert(
+    equal(
+      new Map([["foo", "bar"], ["baz", "qux"]]),
+      new Map([["baz", "qux"], ["foo", "bar"]])
+    )
+  );
+  assert(equal(new Map([["foo", ["bar"]]]), new Map([["foo", ["bar"]]])));
+  assert(!equal(new Map([["foo", "bar"]]), new Map([["bar", "baz"]])));
+  assert(
+    !equal(new Map([["foo", "bar"]]), new Map([["foo", "bar"], ["bar", "baz"]]))
+  );
+  assert(
+    !equal(
+      new Map([["foo", new Map([["bar", "baz"]])]]),
+      new Map([["foo", new Map([["bar", "qux"]])]])
+    )
+  );
 });
 
 test(function testingNotEquals(): void {