Add failing test for tab indentation completion

Author: mxstbr

lib/__tests__/handle-tab.test.js

@@ -61,3 +61,29 @@ it('should replace selected content with the tab', () => {
   expect(toPlainText(before)).toEqual(initialText);
   expect(toPlainText(after)).toEqual(tabs(1));
 });
+
+it('should match the indentation of the previous line', () => {
+  const evt = { preventDefault: jest.fn() };
+  const initialText = `${tabs(2)}const a = 'b';\n`;
+
+  const currentContent = ContentState.createFromText(initialText);
+  // "        const a = 'b'
+  //  "
+  // ^ cursor here (on second line/in second block)
+  const cursorOnSecondLine = SelectionState.createEmpty(
+    currentContent
+      .getBlockMap()
+      .last()
+      .getKey()
+  );
+  const before = EditorState.create({
+    allowUndo: true,
+    currentContent,
+    // Focus the entire initial word
+    selection: cursorOnSecondLine
+  });
+
+  const after = handleTab(evt, before);
+  expect(toPlainText(before)).toEqual(initialText);
+  expect(toPlainText(after)).toEqual(initialText + tabs(2));
+});