Merge pull request #32034 from aaxelb/qunit-rejects

@types/qunit: Add type for qunit's `assert.rejects`

types/qunit/index.d.ts

@@ -236,6 +236,34 @@ interface Assert {
     throws(block: () => void, expected?: any, message?: any): void;
     raises(block: () => void, expected?: any, message?: any): void;
 
+    /**
+     * Test if the provided promise rejects, and optionally compare the
+     * rejection value.
+     *
+     * When testing code that is expected to return a rejected promise based on
+     * a specific set of circumstances, use assert.rejects() for testing and
+     * comparison.
+     *
+     * The expectedMatcher argument can be:
+     *      A function that returns true when the assertion should be considered passing.
+     *      An Error object
+     *      A base constructor to use ala rejectionValue instanceof expectedMatcher
+     *      A RegExp that matches (or partially matches) rejectionValue.toString()
+     *
+     * Note: in order to avoid confusion between the message and the expectedMatcher,
+     * the expectedMatcher can not be a string.
+     *
+     * @param promise promise to test for rejection
+     * @param expectedMatcher Rejection value matcher
+     * @param message A short description of the assertion
+     */
+    rejects(promise: Promise<any>, message?: string): void;
+    rejects(
+        promise: Promise<any>,
+        expectedMatcher?: any,
+        message?: string,
+    ): void;
+
     /**
      * A marker for progress in a given test.
      *

types/qunit/qunit-tests.ts

@@ -562,6 +562,53 @@ QUnit.test( "throws", function( assert ) {
   );
 });
 
+QUnit.test( "rejects", function( assert ) {
+
+  assert.rejects(Promise.reject("some error description"));
+
+  assert.rejects(
+    Promise.reject(new Error("some error description")),
+    "rejects with just a message, not using the 'expectedMatcher' argument"
+  );
+
+  assert.rejects(
+    Promise.reject(new Error("some error description")),
+    /description/,
+    "`rejectionValue.toString()` contains `description`"
+  );
+
+  // Using a custom error like object
+  class CustomError {
+    message?: string;
+    constructor(message?: string) {
+       this.message = message;
+    }
+    toString() {
+       return this.message;
+    }
+  }
+
+  assert.rejects(
+    Promise.reject(new CustomError()),
+    CustomError,
+    "raised error is an instance of CustomError"
+  );
+
+  assert.rejects(
+    Promise.reject(new CustomError("some error description")),
+    new CustomError("some error description"),
+    "raised error instance matches the CustomError instance"
+  );
+
+  assert.rejects(
+    Promise.reject(new CustomError("some error description")),
+    function( err ) {
+      return err.toString() === "some error description";
+    },
+    "raised error instance satisfies the callback function"
+  );
+});
+
 QUnit.module( "module", {
   beforeEach: function( assert ) {
     assert.ok( true, "one extra assert per test" );