[jest-each]: Add empty string/array validation check

CHANGELOG.md

@@ -27,6 +27,7 @@
 
 ### Fixes
 
+- `[jest-each]` Add empty array validation check ([#7249](https://github.com/facebook/jest/pull/7249))
 - `[jest-cli]` Interrupt tests if interactive watch plugin key is pressed ([#7222](https://github.com/facebook/jest/pull/7222))
 - `[jest-cli]` Fix coverage summary reporting ([#7058](https://github.com/facebook/jest/pull/7058))
 - `[jest-each]` Add each array validation check ([#7033](https://github.com/facebook/jest/pull/7033))

packages/jest-each/src/__tests__/__snapshots__/array.test.js.snap

@@ -1,54 +1,94 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
+exports[`jest-each .describe throws an error when called with an empty array 1`] = `
+"Error: \`.each\` called with an empty array of table data.
+"
+`;
+
 exports[`jest-each .describe throws an error when not called with an array 1`] = `
 "\`.each\` must be called with an Array or Tagged Template String.
 
 Instead was called with: undefined
 "
 `;
 
+exports[`jest-each .describe.only throws an error when called with an empty array 1`] = `
+"Error: \`.each\` called with an empty array of table data.
+"
+`;
+
 exports[`jest-each .describe.only throws an error when not called with an array 1`] = `
 "\`.each\` must be called with an Array or Tagged Template String.
 
 Instead was called with: undefined
 "
 `;
 
+exports[`jest-each .fdescribe throws an error when called with an empty array 1`] = `
+"Error: \`.each\` called with an empty array of table data.
+"
+`;
+
 exports[`jest-each .fdescribe throws an error when not called with an array 1`] = `
 "\`.each\` must be called with an Array or Tagged Template String.
 
 Instead was called with: undefined
 "
 `;
 
+exports[`jest-each .fit throws an error when called with an empty array 1`] = `
+"Error: \`.each\` called with an empty array of table data.
+"
+`;
+
 exports[`jest-each .fit throws an error when not called with an array 1`] = `
 "\`.each\` must be called with an Array or Tagged Template String.
 
 Instead was called with: undefined
 "
 `;
 
+exports[`jest-each .it throws an error when called with an empty array 1`] = `
+"Error: \`.each\` called with an empty array of table data.
+"
+`;
+
 exports[`jest-each .it throws an error when not called with an array 1`] = `
 "\`.each\` must be called with an Array or Tagged Template String.
 
 Instead was called with: undefined
 "
 `;
 
+exports[`jest-each .it.only throws an error when called with an empty array 1`] = `
+"Error: \`.each\` called with an empty array of table data.
+"
+`;
+
 exports[`jest-each .it.only throws an error when not called with an array 1`] = `
 "\`.each\` must be called with an Array or Tagged Template String.
 
 Instead was called with: undefined
 "
 `;
 
+exports[`jest-each .test throws an error when called with an empty array 1`] = `
+"Error: \`.each\` called with an empty array of table data.
+"
+`;
+
 exports[`jest-each .test throws an error when not called with an array 1`] = `
 "\`.each\` must be called with an Array or Tagged Template String.
 
 Instead was called with: undefined
 "
 `;
 
+exports[`jest-each .test.only throws an error when called with an empty array 1`] = `
+"Error: \`.each\` called with an empty array of table data.
+"
+`;
+
 exports[`jest-each .test.only throws an error when not called with an array 1`] = `
 "\`.each\` must be called with an Array or Tagged Template String.
 

packages/jest-each/src/__tests__/__snapshots__/template.test.js.snap

@@ -1,5 +1,10 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
+exports[`jest-each .describe throws an error when called with an empty string 1`] = `
+"Error: \`.each\` called with an empty tagged template string of table data.
+"
+`;
+
 exports[`jest-each .describe throws error when there are fewer arguments than headings over multiple rows 1`] = `
 "Not enough arguments supplied for given headings:
 <green>a | b | expected</>
@@ -29,6 +34,11 @@ Received:
 Missing <red>2</> arguments"
 `;
 
+exports[`jest-each .describe.only throws an error when called with an empty string 1`] = `
+"Error: \`.each\` called with an empty tagged template string of table data.
+"
+`;
+
 exports[`jest-each .describe.only throws error when there are fewer arguments than headings over multiple rows 1`] = `
 "Not enough arguments supplied for given headings:
 <green>a | b | expected</>
@@ -58,6 +68,11 @@ Received:
 Missing <red>2</> arguments"
 `;
 
+exports[`jest-each .fdescribe throws an error when called with an empty string 1`] = `
+"Error: \`.each\` called with an empty tagged template string of table data.
+"
+`;
+
 exports[`jest-each .fdescribe throws error when there are fewer arguments than headings over multiple rows 1`] = `
 "Not enough arguments supplied for given headings:
 <green>a | b | expected</>
@@ -87,6 +102,11 @@ Received:
 Missing <red>2</> arguments"
 `;
 
+exports[`jest-each .fit throws an error when called with an empty string 1`] = `
+"Error: \`.each\` called with an empty tagged template string of table data.
+"
+`;
+
 exports[`jest-each .fit throws error when there are fewer arguments than headings over multiple rows 1`] = `
 "Not enough arguments supplied for given headings:
 <green>a | b | expected</>
@@ -116,6 +136,11 @@ Received:
 Missing <red>2</> arguments"
 `;
 
+exports[`jest-each .it throws an error when called with an empty string 1`] = `
+"Error: \`.each\` called with an empty tagged template string of table data.
+"
+`;
+
 exports[`jest-each .it throws error when there are fewer arguments than headings over multiple rows 1`] = `
 "Not enough arguments supplied for given headings:
 <green>a | b | expected</>
@@ -145,6 +170,11 @@ Received:
 Missing <red>2</> arguments"
 `;
 
+exports[`jest-each .it.only throws an error when called with an empty string 1`] = `
+"Error: \`.each\` called with an empty tagged template string of table data.
+"
+`;
+
 exports[`jest-each .it.only throws error when there are fewer arguments than headings over multiple rows 1`] = `
 "Not enough arguments supplied for given headings:
 <green>a | b | expected</>
@@ -174,6 +204,11 @@ Received:
 Missing <red>2</> arguments"
 `;
 
+exports[`jest-each .test throws an error when called with an empty string 1`] = `
+"Error: \`.each\` called with an empty tagged template string of table data.
+"
+`;
+
 exports[`jest-each .test throws error when there are fewer arguments than headings over multiple rows 1`] = `
 "Not enough arguments supplied for given headings:
 <green>a | b | expected</>
@@ -203,6 +238,11 @@ Received:
 Missing <red>2</> arguments"
 `;
 
+exports[`jest-each .test.only throws an error when called with an empty string 1`] = `
+"Error: \`.each\` called with an empty tagged template string of table data.
+"
+`;
+
 exports[`jest-each .test.only throws error when there are fewer arguments than headings over multiple rows 1`] = `
 "Not enough arguments supplied for given headings:
 <green>a | b | expected</>

packages/jest-each/src/__tests__/array.test.js

@@ -60,6 +60,19 @@ describe('jest-each', () => {
         ).toThrowErrorMatchingSnapshot();
       });
 
+      test('throws an error when called with an empty array', () => {
+        const globalTestMocks = getGlobalTestMocks();
+        const eachObject = each.withGlobal(globalTestMocks)([]);
+        const testFunction = get(eachObject, keyPath);
+
+        testFunction('expected string', noop);
+        const globalMock = get(globalTestMocks, keyPath);
+
+        expect(() =>
+          globalMock.mock.calls[0][1](),
+        ).toThrowErrorMatchingSnapshot();
+      });
+
       test('calls global with given title', () => {
         const globalTestMocks = getGlobalTestMocks();
         const eachObject = each.withGlobal(globalTestMocks)([[]]);

packages/jest-each/src/__tests__/template.test.js

@@ -83,6 +83,21 @@ describe('jest-each', () => {
         expect(testCallBack).not.toHaveBeenCalled();
       });
 
+      test('throws an error when called with an empty string', () => {
+        const globalTestMocks = getGlobalTestMocks();
+        const eachObject = each.withGlobal(globalTestMocks)`   `;
+        const testFunction = get(eachObject, keyPath);
+        const testCallBack = jest.fn();
+        testFunction('this will blow up :(', testCallBack);
+
+        const globalMock = get(globalTestMocks, keyPath);
+
+        expect(() =>
+          globalMock.mock.calls[0][1](),
+        ).toThrowErrorMatchingSnapshot();
+        expect(testCallBack).not.toHaveBeenCalled();
+      });
+
       test('calls global with given title', () => {
         const globalTestMocks = getGlobalTestMocks();
         const eachObject = each.withGlobal(globalTestMocks)`

packages/jest-each/src/bind.js

@@ -42,6 +42,30 @@ export default (cb: Function, supportsDone: boolean = true) => (...args: any) =>
           throw error;
         });
       }
+
+      if (
+        tableArg.length === 1 &&
+        typeof tableArg[0] === 'string' &&
+        tableArg[0].trim() === ''
+      ) {
+        const error = new ErrorWithStack(
+          'Error: `.each` called with an empty tagged template string of table data.\n',
+          eachBind,
+        );
+        return cb(title, () => {
+          throw error;
+        });
+      }
+
+      if (tableArg.length === 0) {
+        const error = new ErrorWithStack(
+          'Error: `.each` called with an empty array of table data.\n',
+          eachBind,
+        );
+        return cb(title, () => {
+          throw error;
+        });
+      }
       const table: Table = tableArg.every(Array.isArray)
         ? tableArg
         : tableArg.map(entry => [entry]);