Add deprecation assertions

addon-test-support/asserts/deprecations-include.js

@@ -0,0 +1,11 @@
+import { getDeprecations } from '@ember/test-helpers';
+import toAssertionMessage from './utils/to-assertion-message';
+
+export default function deprecationsInclude(expected) {
+  const deprecations = getDeprecations().map(toAssertionMessage);
+  this.pushResult({
+    result: deprecations.indexOf(expected) > -1,
+    actual: deprecations,
+    message: `expected to find \`${expected}\` deprecation`,
+  });
+}

addon-test-support/asserts/deprecations.js

@@ -0,0 +1,24 @@
+import { getDeprecationsDuringCallback } from '@ember/test-helpers';
+import toAssertionMessage from './utils/to-assertion-message';
+
+export default async function deprecations(callback, expectedDeprecations) {
+  const maybeThenable = getDeprecationsDuringCallback(callback);
+
+  const operation = (deprecations) => {
+    this.deepEqual(
+      deprecations.map(toAssertionMessage),
+      expectedDeprecations,
+      'Expected deprecations during test.'
+    );
+  };
+
+  if (
+    typeof maybeThenable === 'object' &&
+    maybeThenable !== null &&
+    typeof maybeThenable.then === 'function'
+  ) {
+    operation(await maybeThenable);
+  } else {
+    operation(maybeThenable);
+  }
+}

addon-test-support/asserts/no-depreactions.js

@@ -0,0 +1,10 @@
+import { getDeprecations } from '@ember/test-helpers';
+import toAssertionMessage from './utils/to-assertion-message';
+
+export default function noDeprecations() {
+  this.deepEqual(
+    getDeprecations().map(toAssertionMessage),
+    [],
+    'Expected no deprecations during test.'
+  );
+}

addon-test-support/asserts/utils/to-assertion-message.js

@@ -0,0 +1,3 @@
+export default function toAssertionMessage(assertion) {
+  return assertion.message;
+}

addon-test-support/index.js

@@ -27,6 +27,16 @@ import { installTestNotIsolatedHook } from './test-isolation-validation';
 
 let waitForSettled = true;
 
+import deprecationsInclude from './asserts/deprecations-include';
+import deprecations from './asserts/deprecations';
+import noDeprecations from './asserts/no-depreactions';
+
+export function setup(assert) {
+  assert.deprecationsInclude = deprecationsInclude;
+  assert.deprecations = deprecations;
+  assert.noDeprecations = noDeprecations;
+}
+
 export function setupTest(hooks, _options) {
   let options =
     _options === undefined