Allow test titles to include array index

CHANGELOG.md

@@ -3,6 +3,7 @@
 ### Features
 
 - `[jest-runner]` print stack trace when `process.exit` is called from user code ([#6714](https://github.com/facebook/jest/pull/6714))
+- `[jest-each]` introduces `%#` option to add index of the test to its title ([#6414](https://github.com/facebook/jest/pull/6414))
 
 ### Fixes
 

docs/GlobalAPI.md

@@ -241,6 +241,7 @@ Use `describe.each` if you keep duplicating the same test suites with different
     - `%f` - Floating point value.
     - `%j` - JSON.
     - `%o` - Object.
+    - `%#` - Index of the test case.
     - `%%` - single percent sign ('%'). This does not consume an argument.
 - `fn`: `Function` the suite of tests to be ran, this is the function that will receive the parameters in each row as function arguments.
 
@@ -488,6 +489,7 @@ Use `test.each` if you keep duplicating the same test with different data. `test
     - `%f` - Floating point value.
     - `%j` - JSON.
     - `%o` - Object.
+    - `%#` - Index of the test case.
     - `%%` - single percent sign ('%'). This does not consume an argument.
 - `fn`: `Function` the test to be ran, this is the function that will receive the parameters in each row as function arguments.
 

packages/jest-each/README.md

@@ -33,6 +33,7 @@ jest-each allows you to provide multiple arguments to your `test`/`describe` whi
   - `%f` - Floating point value.
   - `%j` - JSON.
   - `%o` - Object.
+  - `%#` - Index of the test case.
   - `%%` - single percent sign ('%'). This does not consume an argument.
 - 🖖 Spock like data tables with [Tagged Template Literals](#tagged-template-literal-of-rows)
 
@@ -109,6 +110,7 @@ const each = require('jest-each');
     - `%f` - Floating point value.
     - `%j` - JSON.
     - `%o` - Object.
+    - `%#` - Index of the test case.
     - `%%` - single percent sign ('%'). This does not consume an argument.
 - testFn: `Function` the test logic, this is the function that will receive the parameters of each row as function arguments
 
@@ -130,6 +132,7 @@ const each = require('jest-each');
     - `%f` - Floating point value.
     - `%j` - JSON.
     - `%o` - Object.
+    - `%#` - Index of the test case.
     - `%%` - single percent sign ('%'). This does not consume an argument.
 - suiteFn: `Function` the suite of `test`/`it`s to be ran, this is the function that will receive the parameters in each row as function arguments
 

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

@@ -102,20 +102,20 @@ describe('jest-each', () => {
           ],
         ]);
         const testFunction = get(eachObject, keyPath);
-        testFunction('expected string: %s %d %s %s %d %j %s %j %d %d', noop);
+        testFunction('expected string: %s %d %s %s %d %j %s %j %d %d %#', noop);
 
         const globalMock = get(globalTestMocks, keyPath);
         expect(globalMock).toHaveBeenCalledTimes(2);
         expect(globalMock).toHaveBeenCalledWith(
           `expected string: hello 1 null undefined 1.2 ${JSON.stringify({
             foo: 'bar',
-          })} () => {} [] Infinity NaN`,
+          })} () => {} [] Infinity NaN 0`,
           expectFunction,
         );
         expect(globalMock).toHaveBeenCalledWith(
           `expected string: world 1 null undefined 1.2 ${JSON.stringify({
             baz: 'qux',
-          })} () => {} [] Infinity NaN`,
+          })} () => {} [] Infinity NaN 1`,
           expectFunction,
         );
       });

packages/jest-each/src/bind.js

@@ -21,15 +21,16 @@ const EXPECTED_COLOR = chalk.green;
 const RECEIVED_COLOR = chalk.red;
 const SUPPORTED_PLACEHOLDERS = /%[sdifjoOp%]/g;
 const PRETTY_PLACEHOLDER = '%p';
+const INDEX_PLACEHOLDER = '%#';
 
 export default (cb: Function) => (...args: any) =>
   function eachBind(title: string, test: Function): void {
     if (args.length === 1) {
       const table: Table = args[0].every(Array.isArray)
         ? args[0]
         : args[0].map(entry => [entry]);
-      return table.forEach(row =>
-        cb(arrayFormat(title, ...row), applyRestParams(row, test)),
+      return table.forEach((row, i) =>
+        cb(arrayFormat(title, i, ...row), applyRestParams(row, test)),
       );
     }
 
@@ -76,7 +77,7 @@ const getPrettyIndexes = placeholders =>
     [],
   );
 
-const arrayFormat = (title, ...args) => {
+const arrayFormat = (title, rowIndex, ...args) => {
   const placeholders = title.match(SUPPORTED_PLACEHOLDERS) || [];
   const prettyIndexes = getPrettyIndexes(placeholders);
 
@@ -101,7 +102,7 @@ const arrayFormat = (title, ...args) => {
   );
 
   return util.format(
-    prettyTitle,
+    prettyTitle.replace(INDEX_PLACEHOLDER, rowIndex.toString()),
     ...remainingArgs.slice(0, placeholders.length - prettyIndexes.length),
   );
 };