Better error message when a describe block is empty

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

@@ -19,11 +19,37 @@ Time:        <<REPLACED>>
 Ran all test suites."
 `;
 
+exports[`cannot have describe with no implementation 1`] = `
+"FAIL __tests__/only-constructs.test.js
+  ● Test suite failed to run
+
+    Missing second argument supplied to 'describe'. It must be a callback function.
+
+      1 | 
+    > 2 |     describe('describe, no implementation');
+        |     ^
+      3 |   
+
+      at packages/jest-jasmine2/build/jasmine/Env.js:<<LINE>>:<<COLUMN>>
+      at __tests__/only-constructs.test.js:<<LINE>>:<<COLUMN>>
+
+"
+`;
+
+exports[`cannot have describe with no implementation 2`] = `
+"Test Suites: 1 failed, 1 total
+Tests:       0 total
+Snapshots:   0 total
+Time:        <<REPLACED>>
+Ran all test suites.
+"
+`;
+
 exports[`cannot test with no implementation 1`] = `
 "FAIL __tests__/only-constructs.test.js
   ● Test suite failed to run
 
-    Missing second argument. It must be a callback function.
+    Missing second argument supplied to 'it'. It must be a callback function.
 
       1 | 
       2 |     it('it', () => {});
@@ -50,7 +76,7 @@ exports[`cannot test with no implementation with expand arg 1`] = `
 "FAIL __tests__/only-constructs.test.js
   ● Test suite failed to run
 
-    Missing second argument. It must be a callback function.
+    Missing second argument supplied to 'it'. It must be a callback function.
 
       1 | 
       2 |     it('it', () => {});

e2e/__tests__/globals.test.js

@@ -112,6 +112,21 @@ test('only', () => {
   expect(summary).toMatchSnapshot();
 });
 
+test('cannot have describe with no implementation', () => {
+  const filename = 'only-constructs.test.js';
+  const content = `
+    describe('describe, no implementation');
+  `;
+
+  writeFiles(TEST_DIR, {[filename]: content});
+  const {stderr, status} = runJest(DIR);
+  expect(status).toBe(1);
+
+  const {summary, rest} = extractSummary(stderr, {stripLocation: true});
+  expect(rest).toMatchSnapshot();
+  expect(summary).toMatchSnapshot();
+});
+
 test('cannot test with no implementation', () => {
   const filename = 'only-constructs.test.js';
   const content = `

packages/jest-jasmine2/src/__tests__/it_test_error.test.js

@@ -12,7 +12,9 @@ describe('test/it error throwing', () => {
   it(`it throws error with missing callback function`, () => {
     expect(() => {
       it('test1');
-    }).toThrowError('Missing second argument. It must be a callback function.');
+    }).toThrowError(
+      "Missing second argument supplied to 'it'. It must be a callback function.",
+    );
   });
   it(`it throws an error when first argument isn't a string`, () => {
     expect(() => {
@@ -23,13 +25,15 @@ describe('test/it error throwing', () => {
     expect(() => {
       it('test3', 'test3b');
     }).toThrowError(
-      `Invalid second argument, test3b. It must be a callback function.`,
+      "Invalid second argument supplied to 'it', test3b. It must be a callback function.",
     );
   });
   test(`test throws error with missing callback function`, () => {
     expect(() => {
       test('test4');
-    }).toThrowError('Missing second argument. It must be a callback function.');
+    }).toThrowError(
+      "Missing second argument supplied to 'it'. It must be a callback function.",
+    );
   });
   test(`test throws an error when first argument isn't a string`, () => {
     expect(() => {
@@ -40,7 +44,7 @@ describe('test/it error throwing', () => {
     expect(() => {
       test('test6', 'test6b');
     }).toThrowError(
-      `Invalid second argument, test6b. It must be a callback function.`,
+      "Invalid second argument supplied to 'it', test6b. It must be a callback function.",
     );
   });
 });

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

@@ -322,6 +322,16 @@ export default function(j$) {
 
     this.describe = function(description, specDefinitions) {
       const suite = suiteFactory(description);
+      if (specDefinitions === undefined) {
+        throw new Error(
+          `Missing second argument supplied to 'describe'. It must be a callback function.`,
+        );
+      }
+      if (typeof specDefinitions !== 'function') {
+        throw new Error(
+          `Invalid second argument supplied to 'describe', ${specDefinitions}. It must be a callback function.`,
+        );
+      }
       if (specDefinitions.length > 0) {
         throw new Error('describe does not expect any arguments');
       }
@@ -450,12 +460,12 @@ export default function(j$) {
       }
       if (fn === undefined) {
         throw new Error(
-          'Missing second argument. It must be a callback function.',
+          `Missing second argument supplied to 'it'. It must be a callback function.`,
         );
       }
       if (typeof fn !== 'function') {
         throw new Error(
-          `Invalid second argument, ${fn}. It must be a callback function.`,
+          `Invalid second argument supplied to 'it', ${fn}. It must be a callback function.`,
         );
       }
       const spec = specFactory(