add stack trace on expect.(has)Assertions (#5997)

* add stack trace on expect.(has)Assertions

* guard against missing `Error.captureStackTrace`

* please flow gods

Author: SimenB

CHANGELOG.md

@@ -72,6 +72,8 @@
 
 ### Fixes
 
+* `[expect]` Add stack trace when `expect.assertions` and `expect.hasAssertions`
+  causes test failures. ([#5997](https://github.com/facebook/jest/pull/5997))
 * `[jest-runtime]` Throw a more useful error when trying to require modules
   after the test environment is torn down
   ([#5888](https://github.com/facebook/jest/pull/5888))

integration-tests/__tests__/__snapshots__/failures.test.js.snap

@@ -36,37 +36,87 @@ exports[`not throwing Error objects 4`] = `
     ✕ throws on assertion
   .hasAssertions()
     ✕ throws when there are not assertions
+
   ● .assertions() › throws
+
     expect(received).toBeTruthy()
+    
     Received: false
+
       11 | const throws = () => {
       12 |   expect.assertions(2);
     > 13 |   expect(false).toBeTruthy();
          |                 ^
       14 | };
       15 | const redeclare = () => {
       16 |   expect.assertions(1);
+      
       at __tests__/assertion_count.test.js:13:17
+
   ● .assertions() › throws
+
     expect.assertions(2)
+    
     Expected two assertions to be called but received one assertion call.
+
+      10 | 
+      11 | const throws = () => {
+    > 12 |   expect.assertions(2);
+         |          ^
+      13 |   expect(false).toBeTruthy();
+      14 | };
+      15 | const redeclare = () => {
+      
+      at __tests__/assertion_count.test.js:12:10
+
   ● .assertions() › throws on redeclare of assertion count
+
     expect(received).toBeTruthy()
+    
     Received: false
+
       15 | const redeclare = () => {
       16 |   expect.assertions(1);
     > 17 |   expect(false).toBeTruthy();
          |                 ^
       18 |   expect.assertions(2);
       19 | };
-      20 |
+      20 | 
+      
       at __tests__/assertion_count.test.js:17:17
+
   ● .assertions() › throws on assertion
+
     expect.assertions(0)
+    
     Expected zero assertions to be called but received one assertion call.
+
+      20 | 
+      21 | const noAssertions = () => {
+    > 22 |   expect.assertions(0);
+         |          ^
+      23 |   expect(true).toBeTruthy();
+      24 | };
+      25 | 
+      
+      at __tests__/assertion_count.test.js:22:10
+
   ● .hasAssertions() › throws when there are not assertions
+
     expect.hasAssertions()
+    
     Expected at least one assertion to be called but received none.
+
+      25 | 
+      26 | const hasNoAssertions = () => {
+    > 27 |   expect.hasAssertions();
+         |          ^
+      28 | };
+      29 | 
+      30 | describe('.assertions()', () => {
+      
+      at __tests__/assertion_count.test.js:27:10
+
 "
 `;
 

integration-tests/__tests__/failures.test.js

@@ -18,30 +18,6 @@ const normalizeDots = text => text.replace(/\.{1,}$/gm, '.');
 
 SkipOnWindows.suite();
 
-const cleanupStackTrace = stderr => {
-  const STACK_REGEXP = /^.*at.*(setup-jest-globals|extractExpectedAssertionsErrors).*\n/gm;
-  if (!STACK_REGEXP.test(stderr)) {
-    throw new Error(
-      `
-      This function is used to remove inconsistent stack traces between
-      jest-jasmine2 and jest-circus. If you see this error, that means the
-      stack traces are no longer inconsistent and this function can be
-      safely removed.
-
-      output:
-      ${stderr}
-    `,
-    );
-  }
-
-  return (
-    stderr
-      .replace(STACK_REGEXP, '')
-      // Also remove trailing whitespace.
-      .replace(/\s+$/gm, '')
-  );
-};
-
 test('not throwing Error objects', () => {
   let stderr;
   stderr = runJest(dir, ['throw_number.test.js']).stderr;
@@ -51,7 +27,7 @@ test('not throwing Error objects', () => {
   stderr = runJest(dir, ['throw_object.test.js']).stderr;
   expect(extractSummary(stderr).rest).toMatchSnapshot();
   stderr = runJest(dir, ['assertion_count.test.js']).stderr;
-  expect(extractSummary(cleanupStackTrace(stderr)).rest).toMatchSnapshot();
+  expect(extractSummary(stderr).rest).toMatchSnapshot();
   stderr = runJest(dir, ['during_tests.test.js']).stderr;
   expect(extractSummary(stderr).rest).toMatchSnapshot();
 });

packages/expect/src/extract_expected_assertions_errors.js

@@ -25,13 +25,15 @@ const resetAssertionsLocalState = () => {
 };
 
 // Create and format all errors related to the mismatched number of `expect`
-// calls and reset the matchers state.
+// calls and reset the matcher's state.
 const extractExpectedAssertionsErrors = () => {
   const result = [];
   const {
     assertionCalls,
     expectedAssertionsNumber,
+    expectedAssertionsNumberError,
     isExpectingAssertions,
+    isExpectingAssertionsError,
   } = getState();
 
   resetAssertionsLocalState();
@@ -43,34 +45,36 @@ const extractExpectedAssertionsErrors = () => {
     const numOfAssertionsExpected = EXPECTED_COLOR(
       pluralize('assertion', expectedAssertionsNumber),
     );
-    const error = new Error(
+
+    expectedAssertionsNumberError.message =
       matcherHint('.assertions', '', String(expectedAssertionsNumber), {
         isDirectExpectCall: true,
       }) +
-        '\n\n' +
-        `Expected ${numOfAssertionsExpected} to be called but received ` +
-        RECEIVED_COLOR(pluralize('assertion call', assertionCalls || 0)) +
-        '.',
-    );
+      '\n\n' +
+      `Expected ${numOfAssertionsExpected} to be called but received ` +
+      RECEIVED_COLOR(pluralize('assertion call', assertionCalls || 0)) +
+      '.';
+
     result.push({
       actual: assertionCalls,
-      error,
+      error: expectedAssertionsNumberError,
       expected: expectedAssertionsNumber,
     });
   }
   if (isExpectingAssertions && assertionCalls === 0) {
     const expected = EXPECTED_COLOR('at least one assertion');
     const received = RECEIVED_COLOR('received none');
-    const error = new Error(
+
+    isExpectingAssertionsError.message =
       matcherHint('.hasAssertions', '', '', {
         isDirectExpectCall: true,
       }) +
-        '\n\n' +
-        `Expected ${expected} to be called but ${received}.`,
-    );
+      '\n\n' +
+      `Expected ${expected} to be called but ${received}.`;
+
     result.push({
       actual: 'none',
-      error,
+      error: isExpectingAssertionsError,
       expected: 'at least one',
     });
   }

packages/expect/src/index.js

@@ -335,19 +335,34 @@ const _validateResult = result => {
   }
 };
 
+function assertions(expected: number) {
+  const error = new Error();
+  if (Error.captureStackTrace) {
+    Error.captureStackTrace(error, assertions);
+  }
+
+  getState().expectedAssertionsNumber = expected;
+  getState().expectedAssertionsNumberError = error;
+}
+function hasAssertions(...args) {
+  const error = new Error();
+  if (Error.captureStackTrace) {
+    Error.captureStackTrace(error, hasAssertions);
+  }
+
+  utils.ensureNoExpected(args[0], '.hasAssertions');
+  getState().isExpectingAssertions = true;
+  getState().isExpectingAssertionsError = error;
+}
+
 // add default jest matchers
 setMatchers(matchers, true, expect);
 setMatchers(spyMatchers, true, expect);
 setMatchers(toThrowMatchers, true, expect);
 
 expect.addSnapshotSerializer = () => void 0;
-expect.assertions = (expected: number) => {
-  getState().expectedAssertionsNumber = expected;
-};
-expect.hasAssertions = (expected: any) => {
-  utils.ensureNoExpected(expected, '.hasAssertions');
-  getState().isExpectingAssertions = true;
-};
+expect.assertions = assertions;
+expect.hasAssertions = hasAssertions;
 expect.getState = getState;
 expect.setState = setState;
 expect.extractExpectedAssertionsErrors = extractExpectedAssertionsErrors;