feat: support async functions in toThrow

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ### Features
 
+- `[expect]` Support `async function`s in `toThrow` ([#9817](https://github.com/facebook/jest/pull/9817))
 - `[jest-console]` Add code frame to `console.error` and `console.warn` ([#9741](https://github.com/facebook/jest/pull/9741))
 - `[@jest/globals]` New package so Jest's globals can be explicitly imported ([#9801](https://github.com/facebook/jest/pull/9801))
 

packages/expect/src/__tests__/__snapshots__/matchers.test.js.snap

@@ -10,7 +10,7 @@ Resolved to value: <r>4</>
 exports[`.rejects fails non-promise value "a" 1`] = `
 <d>expect(</><r>received</><d>).</>rejects<d>.</>toBeDefined<d>()</>
 
-<b>Matcher error</>: <r>received</> value must be a promise
+<b>Matcher error</>: <r>received</> value must be a promise or a function returning a promise
 
 Received has type:  string
 Received has value: <r>"a"</>
@@ -19,7 +19,7 @@ Received has value: <r>"a"</>
 exports[`.rejects fails non-promise value [1] 1`] = `
 <d>expect(</><r>received</><d>).</>rejects<d>.</>toBeDefined<d>()</>
 
-<b>Matcher error</>: <r>received</> value must be a promise
+<b>Matcher error</>: <r>received</> value must be a promise or a function returning a promise
 
 Received has type:  array
 Received has value: <r>[1]</>
@@ -28,7 +28,7 @@ Received has value: <r>[1]</>
 exports[`.rejects fails non-promise value [Function anonymous] 1`] = `
 <d>expect(</><r>received</><d>).</>rejects<d>.</>toBeDefined<d>()</>
 
-<b>Matcher error</>: <r>received</> value must be a promise
+<b>Matcher error</>: <r>received</> value must be a promise or a function returning a promise
 
 Received has type:  function
 Received has value: <r>[Function anonymous]</>
@@ -37,7 +37,7 @@ Received has value: <r>[Function anonymous]</>
 exports[`.rejects fails non-promise value {"a": 1} 1`] = `
 <d>expect(</><r>received</><d>).</>rejects<d>.</>toBeDefined<d>()</>
 
-<b>Matcher error</>: <r>received</> value must be a promise
+<b>Matcher error</>: <r>received</> value must be a promise or a function returning a promise
 
 Received has type:  object
 Received has value: <r>{"a": 1}</>
@@ -46,7 +46,7 @@ Received has value: <r>{"a": 1}</>
 exports[`.rejects fails non-promise value 4 1`] = `
 <d>expect(</><r>received</><d>).</>rejects<d>.</>not<d>.</>toBeDefined<d>()</>
 
-<b>Matcher error</>: <r>received</> value must be a promise
+<b>Matcher error</>: <r>received</> value must be a promise or a function returning a promise
 
 Received has type:  number
 Received has value: <r>4</>
@@ -55,15 +55,15 @@ Received has value: <r>4</>
 exports[`.rejects fails non-promise value null 1`] = `
 <d>expect(</><r>received</><d>).</>rejects<d>.</>not<d>.</>toBeDefined<d>()</>
 
-<b>Matcher error</>: <r>received</> value must be a promise
+<b>Matcher error</>: <r>received</> value must be a promise or a function returning a promise
 
 Received has value: <r>null</>
 `;
 
 exports[`.rejects fails non-promise value true 1`] = `
 <d>expect(</><r>received</><d>).</>rejects<d>.</>not<d>.</>toBeDefined<d>()</>
 
-<b>Matcher error</>: <r>received</> value must be a promise
+<b>Matcher error</>: <r>received</> value must be a promise or a function returning a promise
 
 Received has type:  boolean
 Received has value: <r>true</>
@@ -72,7 +72,7 @@ Received has value: <r>true</>
 exports[`.rejects fails non-promise value undefined 1`] = `
 <d>expect(</><r>received</><d>).</>rejects<d>.</>not<d>.</>toBeDefined<d>()</>
 
-<b>Matcher error</>: <r>received</> value must be a promise
+<b>Matcher error</>: <r>received</> value must be a promise or a function returning a promise
 
 Received has value: <r>undefined</>
 `;

packages/expect/src/__tests__/matchers.test.js

@@ -56,6 +56,12 @@ describe('.rejects', () => {
     await jestExpect(fn()).rejects.toThrow('some error');
   });
 
+  it('should reject async function to toThrow', async () => {
+    await expect(async () => {
+      throw new Error('Test');
+    }).rejects.toThrow('Test');
+  });
+
   ['a', [1], () => {}, {a: 1}].forEach(value => {
     it(`fails non-promise value ${stringify(value)} synchronously`, () => {
       let error;

packages/expect/src/index.ts

@@ -189,19 +189,24 @@ const makeRejectMatcher = (
   matcherName: string,
   matcher: RawMatcherFn,
   isNot: boolean,
-  actual: Promise<any>,
+  actual: Promise<any> | (() => Promise<any>),
   outerErr: JestAssertionError,
 ): PromiseMatcherFn => (...args) => {
   const options = {
     isNot,
     promise: 'rejects',
   };
 
-  if (!isPromise(actual)) {
+  const actualWrapper: Promise<any> =
+    typeof actual === 'function' ? actual() : actual;
+
+  if (!isPromise(actualWrapper)) {
     throw new JestAssertionError(
       matcherUtils.matcherErrorMessage(
         matcherUtils.matcherHint(matcherName, undefined, '', options),
-        `${matcherUtils.RECEIVED_COLOR('received')} value must be a promise`,
+        `${matcherUtils.RECEIVED_COLOR(
+          'received',
+        )} value must be a promise or a function returning a promise`,
         matcherUtils.printWithType(
           'Received',
           actual,
@@ -213,7 +218,7 @@ const makeRejectMatcher = (
 
   const innerErr = new JestAssertionError();
 
-  return actual.then(
+  return actualWrapper.then(
     result => {
       outerErr.message =
         matcherUtils.matcherHint(matcherName, undefined, '', options) +