fix(expect): improve the error message when nothing is thrown when te…

…sting `toThrow` (#3979)

packages/expect/src/jest-expect.ts

@@ -512,12 +512,22 @@ export const JestChaiExpect: ChaiPlugin = (chai, utils) => {
       }
     }
     else {
+      let isThrow = false
       try {
         obj()
       }
       catch (err) {
+        isThrow = true
         thrown = err
       }
+
+      if (!isThrow && !isNot) {
+        const message = utils.flag(this, 'message') || 'expected function to throw an error, but it didn\'t'
+        const error = {
+          showDiff: false,
+        }
+        throw new AssertionError(message, error, utils.flag(this, 'ssfi'))
+      }
     }
 
     if (typeof expected === 'function') {

test/core/test/jest-expect.test.ts

@@ -368,6 +368,22 @@ describe('jest-expect', () => {
       },
     ])
   })
+
+  describe('toThrow', () => {
+    it('error wasn\'t thrown', () => {
+      expect(() => {
+        expect(() => {
+        }).toThrow(Error)
+      }).toThrowErrorMatchingInlineSnapshot('"expected function to throw an error, but it didn\'t"')
+    })
+
+    it('async wasn\'t awaited', () => {
+      expect(() => {
+        expect(async () => {
+        }).toThrow(Error)
+      }).toThrowErrorMatchingInlineSnapshot('"expected function to throw an error, but it didn\'t"')
+    })
+  })
 })
 
 describe('.toStrictEqual()', () => {