diff --git a/frontend/src/__tests__/esp32-integration.test.ts b/frontend/src/__tests__/esp32-integration.test.ts
index c44c36ea..88d79716 100644
--- a/frontend/src/__tests__/esp32-integration.test.ts
+++ b/frontend/src/__tests__/esp32-integration.test.ts
@@ -46,6 +46,7 @@ vi.mock('../simulation/PinManager', () => ({
     this.updatePort = vi.fn();
     this.onPinChange = vi.fn().mockReturnValue(() => {});
     this.getListenersCount = vi.fn().mockReturnValue(0);
+    this.resetPinStates = vi.fn();
   }),
 }));
 
diff --git a/frontend/src/__tests__/esp32c3-blink.test.ts b/frontend/src/__tests__/esp32c3-blink.test.ts
index 031e74d7..7838e4f9 100644
--- a/frontend/src/__tests__/esp32c3-blink.test.ts
+++ b/frontend/src/__tests__/esp32c3-blink.test.ts
@@ -158,9 +158,11 @@ describe('ESP32-C3 bare-metal blink (compiled with riscv32-esp-elf-gcc)', () =>
     sim.loadBin(binData);
     runSteps(sim, 2000);
 
-    // PinManager must have received GPIO 8 state changes
-    expect(pm.setPinState).toHaveBeenCalledWith(8, true);
-    expect(pm.setPinState).toHaveBeenCalledWith(8, false);
+    // PinManager must have received GPIO 8 state changes. Production code
+    // passes the optional `source` argument ('mcu') since PinManager added
+    // the input/output classification field.
+    expect(pm.setPinState).toHaveBeenCalledWith(8, true, 'mcu');
+    expect(pm.setPinState).toHaveBeenCalledWith(8, false, 'mcu');
   });
 
   it('timestamps increase monotonically across blink events', () => {
diff --git a/frontend/src/__tests__/esp32c3-simulation.test.ts b/frontend/src/__tests__/esp32c3-simulation.test.ts
index 6d8ebc48..7b06abf2 100644
--- a/frontend/src/__tests__/esp32c3-simulation.test.ts
+++ b/frontend/src/__tests__/esp32c3-simulation.test.ts
@@ -480,7 +480,7 @@ describe('Esp32C3Simulator — GPIO pin toggling', () => {
     core.reset(0x42000000);
     runSteps(core, 3);
 
-    expect(pm.setPinState).toHaveBeenCalledWith(0, true);
+    expect(pm.setPinState).toHaveBeenCalledWith(0, true, 'mcu');
     s.stop();
   });
 });
diff --git a/frontend/src/__tests__/multi-board-integration.test.ts b/frontend/src/__tests__/multi-board-integration.test.ts
index 32bea691..42e26c1b 100644
--- a/frontend/src/__tests__/multi-board-integration.test.ts
+++ b/frontend/src/__tests__/multi-board-integration.test.ts
@@ -48,6 +48,7 @@ vi.mock('../simulation/PinManager', () => ({
     this.updatePort = vi.fn();
     this.onPinChange = vi.fn().mockReturnValue(() => {});
     this.getListenersCount = vi.fn().mockReturnValue(0);
+    this.resetPinStates = vi.fn();
   }),
 }));