test: add unit tests for tempo.js

Author: Inuth0603

js/widgets/tempo.js

@@ -438,3 +438,6 @@ class Tempo {
         return this._save_lock;
     }
 }
+if (typeof module !== "undefined") {
+    module.exports = Tempo;
+}

js/widgets/tempo.test.js

@@ -0,0 +1,121 @@
+const Tempo = require("./tempo.js");
+
+// --- 1. Global Mocks (Fake the Browser Environment) ---
+global._ = (msg) => msg; // Mock translation function
+global.getDrumSynthName = jest.fn();
+
+// Mock the Window Manager
+global.window = {
+    widgetWindows: {
+        windowFor: jest.fn().mockReturnValue({
+            clear: jest.fn(),
+            show: jest.fn(),
+            addButton: jest.fn().mockReturnValue({ onclick: () => {} }),
+            addInputButton: jest.fn().mockImplementation((val) => ({
+                value: val,
+                addEventListener: jest.fn()
+            })),
+            getWidgetBody: jest.fn().mockReturnValue({
+                appendChild: jest.fn(),
+                insertRow: jest.fn().mockReturnValue({
+                    insertCell: jest.fn().mockReturnValue({
+                        appendChild: jest.fn(),
+                        setAttribute: jest.fn()
+                    })
+                })
+            }),
+            sendToCenter: jest.fn()
+        })
+    }
+};
+
+// Mock Document (for creating the canvas)
+global.document = {
+    createElement: jest.fn().mockReturnValue({
+        style: {},
+        getContext: jest.fn().mockReturnValue({
+            clearRect: jest.fn(),
+            beginPath: jest.fn(),
+            fillStyle: "",
+            ellipse: jest.fn(),
+            fill: jest.fn(),
+            closePath: jest.fn()
+        })
+    })
+};
+
+describe("Tempo Widget", () => {
+    let tempoWidget;
+    let mockActivity;
+
+    beforeEach(() => {
+        tempoWidget = new Tempo();
+
+        // Mock the Music Blocks Activity object
+        mockActivity = {
+            logo: {
+                synth: { loadSynth: jest.fn() },
+                firstNoteTime: 1000
+            },
+            blocks: {
+                blockList: {}, // Empty block list for now
+                loadNewBlocks: jest.fn()
+            },
+            refreshCanvas: jest.fn(),
+            saveLocally: jest.fn(),
+            textMsg: jest.fn(),
+            errorMsg: jest.fn() // This is what the code calls!
+        };
+
+        // --- FIX 1: Set the Global 'activity' variable ---
+        // The widget code calls 'activity.errorMsg', relying on it being global.
+        global.activity = mockActivity;
+
+        // Manually setup initial state usually handled by init()
+        tempoWidget.activity = mockActivity;
+        tempoWidget.BPMs = [100]; // Start at 100 BPM
+        tempoWidget.BPMInputs = [{ value: 100 }]; // Fake input element
+        tempoWidget._intervals = [600];
+        tempoWidget.BPMBlocks = [null];
+        
+        // --- FIX 2: Initialize 'isMoving' ---
+        tempoWidget.isMoving = true; 
+    });
+
+    test("should initialize with default values", () => {
+        expect(tempoWidget.BPMs[0]).toBe(100);
+        expect(tempoWidget.isMoving).toBe(true);
+    });
+
+    test("speedUp() should increase BPM by 10%", () => {
+        // 100 + 10% = 110
+        tempoWidget.speedUp(0);
+        expect(tempoWidget.BPMs[0]).toBe(110);
+        expect(tempoWidget.BPMInputs[0].value).toBe(110);
+    });
+
+    test("slowDown() should decrease BPM by 10%", () => {
+        // 100 - 10% = 90
+        tempoWidget.slowDown(0);
+        expect(tempoWidget.BPMs[0]).toBe(90);
+        expect(tempoWidget.BPMInputs[0].value).toBe(90);
+    });
+
+    test("should not exceed maximum BPM of 1000", () => {
+        tempoWidget.BPMs[0] = 950;
+        // 950 + 95 = 1045 -> Should clamp to 1000
+        tempoWidget.speedUp(0);
+        
+        expect(tempoWidget.BPMs[0]).toBe(1000);
+        expect(mockActivity.errorMsg).toHaveBeenCalled();
+    });
+
+    test("should not go below minimum BPM of 30", () => {
+        tempoWidget.BPMs[0] = 32;
+        // 32 - 3.2 = 28.8 -> Should clamp to 30
+        tempoWidget.slowDown(0);
+
+        expect(tempoWidget.BPMs[0]).toBe(30);
+        expect(mockActivity.errorMsg).toHaveBeenCalled();
+    });
+});