docs(testing): add module docs

testing/README.md

@@ -5,3 +5,30 @@ This package provides utilities for testing.
 - [Faking time and timers](https://jsr.io/@std/testing/doc/time/~)
 - [Snapshot testing](https://jsr.io/@std/testing/doc/snapshot/~)
 - [Type assertions](https://jsr.io/@std/testing/doc/types/~)
+
+```ts
+import { assertSpyCalls, spy } from "@std/testing/mock";
+import { FakeTime } from "@std/testing/time";
+
+function secondInterval(cb: () => void): number {
+  return setInterval(cb, 1000);
+}
+
+Deno.test("secondInterval calls callback every second and stops after being cleared", () => {
+  using time = new FakeTime();
+
+  const cb = spy();
+  const intervalId = secondInterval(cb);
+  assertSpyCalls(cb, 0);
+  time.tick(500);
+  assertSpyCalls(cb, 0);
+  time.tick(500);
+  assertSpyCalls(cb, 1);
+  time.tick(3500);
+  assertSpyCalls(cb, 4);
+
+  clearInterval(intervalId);
+  time.tick(1000);
+  assertSpyCalls(cb, 4);
+});
+```

testing/types.ts

@@ -1,6 +1,24 @@
 // Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
 // Copyright @dsherret and dsherret/conditional-type-checks contributors. All rights reserved. MIT license.
 
+/**
+ * Testing utilities for types.
+ *
+ * ```ts ignore
+ * import { assertType, IsExact, IsNullable } from "@std/testing/types";
+ *
+ * const result = "some result" as string | number;
+ *
+ * // compile error if the type of `result` is not exactly `string | number`
+ * assertType<IsExact<typeof result, string | number>>(true);
+ *
+ * // causes a compile error that `true` is not assignable to `false`
+ * assertType<IsNullable<string>>(true); // error: string is not nullable
+ * ```
+ *
+ * @module
+ */
+
 /**
  * Asserts at compile time that the provided type argument's type resolves to the expected boolean literal type.
  *