fix: show stack traces on async assert errors

CHANGELOG.md

@@ -21,6 +21,7 @@
 - `[jest-cli]` Update jest-cli to show git ref in message when using `changedSince` ([#7028](https://github.com/facebook/jest/pull/7028))
 - `[jest-jasmine2`] Fix crash when test return Promise rejected with null ([#7049](https://github.com/facebook/jest/pull/7049))
 - `[jest-runtime]` Check `_isMockFunction` is true rather than truthy on potential global mocks ([#7017](https://github.com/facebook/jest/pull/7017))
+- `[jest-jasmine]` Show proper error message from async `assert` errors ([#6821](https://github.com/facebook/jest/pull/6821))
 
 ### Chore & Maintenance
 

e2e/__tests__/__snapshots__/failures.test.js.snap

@@ -456,6 +456,7 @@ exports[`works with node assert 1`] = `
   ✕ assert.ifError
   ✕ assert.doesNotThrow
   ✕ assert.throws
+  ✕ async
 
   ● assert
 
@@ -809,9 +810,43 @@ exports[`works with node assert 1`] = `
          |          ^
       78 | });
       79 | 
+      80 | test('async', async () => {
 
       at __tests__/node_assertion_error.test.js:77:10
 
+  ● async
+
+    assert.equal(received, expected) or assert(received) 
+
+    Expected value to be equal to:
+      \\"hello\\"
+    Received:
+      \\"hello
+    goodbye\\"
+
+    Message:
+      hmmm
+
+    Difference:
+
+    - Expected
+    + Received
+
+      hello
+    + goodbye
+
+      79 | 
+      80 | test('async', async () => {
+    > 81 |   assert.equal('hello\\\\ngoodbye', 'hello', 'hmmm');
+         |          ^
+      82 | });
+      83 | 
+
+      at __tests__/node_assertion_error.test.js:81:10
+      at __tests__/node_assertion_error.test.js:12:191
+      at __tests__/node_assertion_error.test.js:12:437
+      at __tests__/node_assertion_error.test.js:12:99
+
 "
 `;
 

e2e/failures/__tests__/node_assertion_error.test.js

@@ -76,3 +76,7 @@ test('assert.doesNotThrow', () => {
 test('assert.throws', () => {
   assert.throws(() => {});
 });
+
+test('async', async () => {
+  assert.equal('hello\ngoodbye', 'hello', 'hmmm');
+});

packages/jest-jasmine2/src/jasmine/Env.js

@@ -30,9 +30,11 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
 /* eslint-disable sort-keys */
 
+import {AssertionError} from 'assert';
 import queueRunner from '../queue_runner';
 import treeProcessor from '../tree_processor';
 import checkIsError from '../is_error';
+import assertionErrorMessage from '../assert_support';
 
 // Try getting the real promise object from the context, if available. Someone
 // could have overridden it in a test. Async functions return it implicitly.
@@ -547,7 +549,18 @@ export default function(j$) {
     };
 
     this.fail = function(error) {
-      const {isError, message} = checkIsError(error);
+      let isError;
+      let message;
+
+      if (error instanceof AssertionError) {
+        isError = false;
+        message = assertionErrorMessage(error, {expand: j$.Spec.expand});
+      } else {
+        const check = checkIsError(error);
+
+        isError = check.isError;
+        message = check.message;
+      }
 
       currentRunnable().addExpectationResult(false, {
         matcherName: '',