Add assert-methods.js module

- This is used to patch in helper methods into the global assert object such as `rejects()` for testing.
- The new rejects method gives tests the ability to easily test error results in async methods that return a promise.
- Replace all async try/catch tests with assert.rejects
Signed-off-by: Kyle Keating <kkeating@hypothes.is>

src/sidebar/services/test/annotations-test.js

@@ -244,12 +244,7 @@ describe('annotationsService', () => {
       fakeApi.annotation.delete.rejects(new Error('Annotation does not exist'));
       const annot = fixtures.defaultAnnotation();
 
-      try {
-        await svc.delete(annot);
-      } catch (e) {
-        /* Ignored */
-      }
-
+      await assert.rejects(svc.delete(annot), 'Annotation does not exist');
       assert.notCalled(fakeStore.removeAnnotations);
     });
   });
@@ -271,12 +266,7 @@ describe('annotationsService', () => {
       fakeApi.annotation.flag.rejects(new Error('Annotation does not exist'));
       const annot = fixtures.defaultAnnotation();
 
-      try {
-        await svc.flag(annot);
-      } catch (e) {
-        /* Ignored */
-      }
-
+      await assert.rejects(svc.flag(annot), 'Annotation does not exist');
       assert.notCalled(fakeStore.updateFlagStatus);
     });
   });

src/sidebar/test/bootstrap.js

 // Expose the sinon assertions.
 sinon.assert.expose(assert, { prefix: null });
 
+// Patch extra assert helper methods
+import patch from '../../test-util/assert-methods';
+patch(assert);
+
 import 'angular';
 import 'angular-mocks';
 

src/sidebar/util/test/fetch-config-test.js

-import { assertPromiseIsRejected } from '../../../shared/test/promise-util';
 import { fetchConfig, $imports } from '../fetch-config';
 
 describe('sidebar.util.fetch-config', () => {
@@ -108,18 +107,18 @@ describe('sidebar.util.fetch-config', () => {
         });
       });
 
-      it('rejects if sidebar is top frame', () => {
+      it('rejects if sidebar is top frame', async () => {
         fakeWindow.parent = fakeWindow;
         fakeWindow.top = fakeWindow;
-
-        const config = fetchConfig({}, fakeWindow);
-        return assertPromiseIsRejected(config, 'Client is top frame');
+        await assert.rejects(
+          fetchConfig({}, fakeWindow),
+          'Client is top frame'
+        );
       });
 
-      it('rejects if fetching config fails', () => {
+      it('rejects if fetching config fails', async () => {
         fakeJsonRpc.call.returns(Promise.reject(new Error('Nope')));
-        const config = fetchConfig({}, fakeWindow);
-        return assertPromiseIsRejected(config, 'Nope');
+        await assert.rejects(fetchConfig({}, fakeWindow), 'Nope');
       });
 
       it('returns config from ancestor frame', async () => {
@@ -210,15 +209,10 @@ describe('sidebar.util.fetch-config', () => {
             ancestorLevel: 10, // The top window is only 2 levels high
           },
         });
-        try {
-          await fetchConfig({}, fakeWindow);
-          throw new Error('Failed to catch error');
-        } catch (e) {
-          assert.equal(
-            e.message,
-            'The target parent frame has exceeded the ancestor tree. Try reducing the `requestConfigFromFrame.ancestorLevel` value in the `hypothesisConfig`'
+        await assert.rejects(
+          fetchConfig({}, fakeWindow),
+          /The target parent frame has exceeded the ancestor tree|Try reducing the/g
         );
-        }
       });
 
       it('creates a merged config when the RPC requests returns the host config', async () => {
@@ -235,9 +229,7 @@ describe('sidebar.util.fetch-config', () => {
       it('rejects if fetching config fails` ', async () => {
         fakeJsonRpc.call.rejects(new Error('Nope'));
         const appConfig = { foo: 'bar', appType: 'via' };
-
-        const result = fetchConfig(appConfig, fakeWindow);
-        return assertPromiseIsRejected(result, 'Nope');
+        await assert.rejects(fetchConfig(appConfig, fakeWindow), 'Nope');
       });
 
       it('returns the `groups` array with the initial host config request', async () => {
@@ -278,12 +270,10 @@ describe('sidebar.util.fetch-config', () => {
         fakeJsonRpc.call.onFirstCall().resolves({ foo: 'baz' }); // host config
         fakeJsonRpc.call.onSecondCall().rejects(); // requestGroups
         const result = await fetchConfig(appConfig, fakeWindow);
-        try {
-          await result.services[0].groups;
-          throw new Error('Failed to catch error');
-        } catch (e) {
-          assert.equal(e.message, 'Unable to fetch groups');
-        }
+        await assert.rejects(
+          result.services[0].groups,
+          'Unable to fetch groups'
+        );
       });
     });
 
@@ -299,15 +289,10 @@ describe('sidebar.util.fetch-config', () => {
             // missing ancestorLevel
           },
         });
-        try {
-          await fetchConfig({}, fakeWindow);
-          throw new Error('Failed to catch error');
-        } catch (e) {
-          assert.equal(
-            e.message,
+        await assert.rejects(
+          fetchConfig({}, fakeWindow),
           'Improper `requestConfigFromFrame` object. Both `ancestorLevel` and `origin` need to be specified'
         );
-        }
       });
 
       it('missing origin', async () => {
@@ -317,15 +302,10 @@ describe('sidebar.util.fetch-config', () => {
             ancestorLevel: 2,
           },
         });
-        try {
-          await fetchConfig({}, fakeWindow);
-          throw new Error('Failed to catch error');
-        } catch (e) {
-          assert.equal(
-            e.message,
+        await assert.rejects(
+          fetchConfig({}, fakeWindow),
           'Improper `requestConfigFromFrame` object. Both `ancestorLevel` and `origin` need to be specified'
         );
-        }
       });
     });
   });

src/test-util/assert-methods.js

+/**
+ * Add-on for async exception testing.
+ *
+ * The `promiseResult` is awaited, and then upon any exception, the resulting
+ * error message is matched against the `errorMessage` string or regex. This
+ * method throws an error if `promiseResult` does not throw an error or will
+ * throw an assertion error if the caught error message differs from the
+ * `errorMessage` parameter.
+ *
+ * e.g. await rejects(someAsyncFunction(), /expected error/g);
+ *
+ * @param {Promise} promiseResult - The returned promise a function to test
+ * @param errorMessage {RegEx|String} - A string or regex that matches the error
+ * which is expected to be thrown.
+ */
+
+const rejects = async (promiseResult, errorMessage) => {
+  try {
+    await promiseResult;
+    const error = new Error();
+    error.name = 'ErrorNotCaught';
+    throw error;
+  } catch (e) {
+    if (e.name === 'ErrorNotCaught') {
+      throw new Error(
+        'Expected to catch the rejected promise but it was not thrown'
+      );
+    }
+    if (errorMessage instanceof RegExp) {
+      assert.isTrue(errorMessage.test(e.message));
+    } else {
+      assert.equal(errorMessage, e.message);
+    }
+  }
+};
+
+/**
+ * Patches the assert object with additional custom helper methods
+ * defined in this module.
+ *
+ * @param {Object} assert - global assertion object.
+ */
+export default function patch(assert) {
+  assert.rejects = rejects;
+}