expect: Improve report when assertion fails, part 6 (#7621)

* expect: Improve report when assertion fails, part 6

* Fix flow errors

* Move new function to reduce noise in diff

* Update CHANGELOG.md

* Convert ANSI codes in promise/async snapshots

* Rewrite promise/async snapshot tests

* Reduce length of labels and handle non-error values

* Add tests for non-error values

* Fix prettier lint error

* Update ExpectAPI.md

* Improve grammar in ExpectAPI.md

* Delete an exception from Received function did not throw

* Correct typo in ExpectAPI.md

* Correct type and report for non-error class

CHANGELOG.md

@@ -50,6 +50,7 @@
 - `[jest-config]` Allow % based configuration of `--max-workers` ([#7494](https://github.com/facebook/jest/pull/7494))
 - `[jest-runner]` Instantiate the test environment class with the current `testPath` ([#7442](https://github.com/facebook/jest/pull/7442))
 - `[jest-config]` Always resolve jest-environment-jsdom from jest-config ([#7476](https://github.com/facebook/jest/pull/7476))
+- `[expect]` Improve report when assertion fails, part 6 ([#7621](https://github.com/facebook/jest/pull/7621))
 
 ### Fixes
 

docs/ExpectAPI.md

@@ -1168,7 +1168,14 @@ test('throws on octopus', () => {
 });
 ```
 
-If you want to test that a specific error gets thrown, you can provide an argument to `toThrow`. The argument can be a string that should be contained in the error message, a class for the error, or a regex that should match the error message. For example, let's say that `drinkFlavor` is coded like this:
+To test that a specific error is thrown, you can provide an argument:
+
+- regular expression: error message **matches** the pattern
+- string: error message **includes** the substring
+- error object: error message is **equal to** the message property of the object
+- error class: error object is **instance of** class
+
+For example, let's say that `drinkFlavor` is coded like this:
 
 ```js
 function drinkFlavor(flavor) {
@@ -1193,6 +1200,7 @@ test('throws on octopus', () => {
 
   // Test the exact error message
   expect(drinkOctopus).toThrowError(/^yuck, octopus flavor$/);
+  expect(drinkOctopus).toThrowError(new Error('yuck, octopus flavor'));
 
   // Test that we get a DisgustingFlavorError
   expect(drinkOctopus).toThrowError(DisgustingFlavorError);