diff --git a/src/utils/TestUtils.test.ts b/src/utils/TestUtils.test.ts
index 32a7e9bc0..a447c8e85 100644
--- a/src/utils/TestUtils.test.ts
+++ b/src/utils/TestUtils.test.ts
@@ -4,7 +4,7 @@
  */
 
 import { IColorSet, IRenderer, IRenderDimensions, IColorManager } from '../renderer/Types';
-import { IInputHandlingTerminal, IViewport, ICompositionHelper, ITerminal, IBuffer, IBufferSet, IBrowser, ICharMeasure, ISelectionManager, ITerminalOptions, ILinkifier, IMouseHelper, ILinkMatcherOptions, CharacterJoinerHandler, IBufferLine } from '../Types';
+import { IInputHandlingTerminal, IViewport, ICompositionHelper, ITerminal, IBuffer, IBufferSet, IBrowser, ICharMeasure, ISelectionManager, ITerminalOptions, ILinkifier, IMouseHelper, ILinkMatcherOptions, CharacterJoinerHandler, IBufferLine, IBufferStringIterator } from '../Types';
 import { ICircularList, XtermListener } from '../common/Types';
 import { Buffer } from '../Buffer';
 import * as Browser from '../shared/utils/Browser';
@@ -311,6 +311,12 @@ export class MockBuffer implements IBuffer {
   setLines(lines: ICircularList<IBufferLine>): void {
     this.lines = lines;
   }
+  stringIndexToBufferIndex(lineIndex: number, stringIndex: number): number[] {
+    throw new Error('Method not implemented.');
+  }
+  contents(trimRight: boolean, startIndex?: number, endIndex?: number): IBufferStringIterator {
+    throw new Error('Method not implemented.');
+  }
 }
 
 export class MockRenderer implements IRenderer {