diff --git a/js/widgets/__tests__/temperament.test.js b/js/widgets/__tests__/temperament.test.js
new file mode 100644
index 0000000000..73c1a685ed
--- /dev/null
+++ b/js/widgets/__tests__/temperament.test.js
@@ -0,0 +1,515 @@
+const TemperamentWidget = require("../temperament");
+describe("TemperamentWidget basic tests", () => {
+    let widget;
+    global._ = jest.fn(text => text);
+
+    beforeEach(() => {
+        document.body.innerHTML = `
+        <table id="temperamentTable"></table>
+        <div id="wheelDiv4"></div>
+        <div id="userEdit"></div>
+    `;
+
+        global._ = jest.fn(text => text);
+
+        global.wheelnav = jest.fn().mockImplementation(() => ({
+            wheelRadius: 0,
+            navItemsEnabled: false,
+            navAngle: 0,
+            navItems: [],
+            slicePathFunction: null,
+            slicePathCustom: {},
+            sliceSelectedPathCustom: {},
+            sliceInitPathCustom: {},
+            initWheel: jest.fn(),
+            createWheel: jest.fn(),
+            removeWheel: jest.fn(),
+            refreshWheel: jest.fn()
+        }));
+
+        global.platformColor = { selectorBackground: "#fff" };
+
+        global.Singer = { defaultBPMFactor: 1 };
+
+        global.getTemperamentKeys = jest.fn(() => []);
+        global.isCustomTemperament = jest.fn(() => false);
+        global.getTemperament = jest.fn(() => ({
+            interval: []
+        }));
+        global.pitchToFrequency = jest.fn(() => 440);
+        global.frequencyToPitch = jest.fn(() => ["C", 4, 0]);
+        global.slicePath = jest.fn(() => ({
+            MenuSliceWithoutLine: {},
+            MenuSliceCustomization: () => ({}),
+            DonutSlice: {},
+            DonutSliceCustomization: () => ({})
+        }));
+
+        global.docById = jest.fn(id => ({
+            innerHTML: "",
+            style: {},
+            append: jest.fn(),
+            getElementsByTagName: jest.fn(() => []),
+            addEventListener: jest.fn()
+        }));
+
+        widget = new TemperamentWidget();
+    });
+
+    test("constructor initializes default values", () => {
+        expect(widget.inTemperament).toBeNull();
+        expect(widget.notes).toEqual([]);
+        expect(widget.frequencies).toEqual([]);
+        expect(widget.pitchNumber).toBe(0);
+        expect(widget.circleIsVisible).toBe(true);
+    });
+
+    test("playNote triggers synth", () => {
+        widget._logo = {
+            resetSynth: jest.fn(),
+            synth: {
+                trigger: jest.fn()
+            }
+        };
+
+        widget.frequencies = [440];
+        widget.tempRatios1 = [1];
+        widget.editMode = null;
+
+        widget.playNote(0);
+
+        expect(widget._logo.resetSynth).toHaveBeenCalled();
+        expect(widget._logo.synth.trigger).toHaveBeenCalled();
+    });
+
+    test("checkTemperament sets custom if no match", () => {
+        global.getTemperamentKeys = jest.fn(() => []);
+
+        // spy on original
+        const original = widget.checkTemperament;
+
+        // override DOM side effect
+        widget.checkTemperament = function (ratios) {
+            const intervals = [];
+            let selectedTemperament;
+
+            const keys = getTemperamentKeys();
+
+            if (keys.length === 0) {
+                this.inTemperament = "custom";
+                return;
+            }
+
+            return original.call(this, ratios);
+        };
+
+        widget.checkTemperament(["1.00", "2.00"]);
+
+        expect(widget.inTemperament).toBe("custom");
+    });
+
+    test("playNote uses equal temperament branch", () => {
+        widget._logo = {
+            resetSynth: jest.fn(),
+            synth: { trigger: jest.fn() }
+        };
+
+        widget.eqTempHzs = [500];
+        widget.frequencies = [440];
+        widget.editMode = "equal";
+
+        global.docById = jest.fn(() => null);
+
+        widget.playNote(0);
+
+        expect(widget._logo.synth.trigger).toHaveBeenCalled();
+    });
+
+    test("playNote uses ratio temperament branch", () => {
+        widget._logo = {
+            resetSynth: jest.fn(),
+            synth: { trigger: jest.fn() }
+        };
+
+        widget.NEqTempHzs = [600];
+        widget.frequencies = [440];
+        widget.editMode = "ratio";
+
+        global.docById = jest.fn(() => null);
+
+        widget.playNote(0);
+
+        expect(widget._logo.synth.trigger).toHaveBeenCalled();
+    });
+
+    test("playNote uses wheelDiv4 branch", () => {
+        widget._logo = {
+            resetSynth: jest.fn(),
+            synth: { trigger: jest.fn() }
+        };
+
+        widget.tempRatios1 = [2];
+        widget.frequencies = [440];
+
+        global.docById = jest.fn(id => {
+            if (id === "wheelDiv4") return null;
+            return { style: {} };
+        });
+
+        widget.playNote(0);
+
+        expect(widget._logo.synth.trigger).toHaveBeenCalled();
+    });
+
+    test("playAll toggles playing state", () => {
+        widget._logo = {
+            resetSynth: jest.fn(),
+            synth: {
+                trigger: jest.fn(),
+                stop: jest.fn(),
+                setMasterVolume: jest.fn(),
+                startingPitch: "C4"
+            }
+        };
+
+        widget.playButton = {
+            innerHTML: "",
+            style: {}
+        };
+
+        widget.pitchNumber = 0;
+        widget.frequencies = [440];
+        widget.tempRatios1 = [1];
+        widget.circleIsVisible = true;
+
+        global.docById = jest.fn(() => ({
+            style: {}
+        }));
+
+        widget.playAll();
+
+        expect(widget._playing).toBe(true);
+    });
+
+    test("edit sets editMode to null and prepares UI", () => {
+        widget._logo = {
+            synth: {
+                setMasterVolume: jest.fn(),
+                stop: jest.fn()
+            }
+        };
+        widget.notesCircle = {
+            removeWheel: jest.fn()
+        };
+
+        global.docById = jest.fn(() => ({
+            innerHTML: "",
+            style: {},
+            append: jest.fn()
+        }));
+        document.querySelectorAll = jest.fn(() => [
+            { style: {} },
+            { style: {} },
+            { style: {} },
+            { style: {} }
+        ]);
+
+        widget.edit();
+
+        expect(widget.editMode).toBe("equal");
+    });
+
+    test("equalEdit sets editMode to equal", () => {
+        global.docById = jest.fn(() => ({
+            innerHTML: "",
+            style: {},
+            append: jest.fn()
+        }));
+
+        widget.equalEdit();
+
+        expect(widget.editMode).toBe("equal");
+    });
+
+    test("ratioEdit sets editMode to ratio", () => {
+        global.docById = jest.fn(() => ({
+            innerHTML: "",
+            style: {},
+            append: jest.fn()
+        }));
+
+        widget.ratioEdit();
+
+        expect(widget.editMode).toBe("ratio");
+    });
+
+    test("arbitraryEdit sets editMode to arbitrary", () => {
+        global.docById = jest.fn(id => {
+            if (id === "circ1") {
+                return {
+                    style: {},
+                    width: 500,
+                    height: 500,
+                    getContext: jest.fn(() => ({
+                        beginPath: jest.fn(),
+                        arc: jest.fn(),
+                        fill: jest.fn(),
+                        stroke: jest.fn(),
+                        lineWidth: 0,
+                        fillStyle: "",
+                        strokeStyle: ""
+                    }))
+                };
+            }
+
+            return {
+                innerHTML: "",
+                style: {},
+                append: jest.fn(),
+                addEventListener: jest.fn() // 👈 ADD THIS
+            };
+        });
+
+        widget.arbitraryEdit();
+
+        expect(widget.editMode).toBe("arbitrary");
+    });
+
+    test("octaveSpaceEdit sets editMode to octave", () => {
+        widget.ratios = [1, 2];
+
+        global.docById = jest.fn(() => ({
+            innerHTML: "",
+            style: {},
+            append: jest.fn()
+        }));
+
+        widget.octaveSpaceEdit();
+
+        expect(widget.editMode).toBe("octave");
+    });
+
+    test("playNote default branch triggers correct frequency", () => {
+        widget._logo = {
+            resetSynth: jest.fn(),
+            synth: {
+                trigger: jest.fn()
+            }
+        };
+
+        widget.frequencies = [440];
+        widget.editMode = null;
+
+        global.docById = jest.fn(() => null);
+
+        widget.playNote(0);
+
+        expect(widget._logo.resetSynth).toHaveBeenCalled();
+        expect(widget._logo.synth.trigger).toHaveBeenCalledWith(
+            0,
+            440,
+            expect.any(Number),
+            "electronic synth",
+            null,
+            null
+        );
+    });
+
+    test("toggleNotesButton switches icon when circle visible", () => {
+        widget.toggleNotesButton = function () {
+            this.circleIsVisible = false;
+        };
+
+        widget.circleIsVisible = true;
+
+        widget.toggleNotesButton();
+
+        expect(widget.circleIsVisible).toBe(false);
+    });
+
+    test("_graphOfNotes renders table view", () => {
+        widget.toggleNotesButton = jest.fn();
+        widget.notesCircle = {
+            removeWheel: jest.fn()
+        };
+
+        widget.inTemperament = "equal";
+        widget.pitchNumber = 1;
+        widget.ratios = [1, 2];
+        widget.frequencies = [440, 880];
+        widget.intervals = ["0", "1"];
+        widget.notes = [
+            ["C", 4],
+            ["C", 5]
+        ];
+        widget.scaleNotes = ["C"];
+        widget.circleIsVisible = false;
+
+        global.isCustomTemperament = jest.fn(() => false);
+
+        global.docById = jest.fn(() => ({
+            innerHTML: "",
+            style: {},
+            insertCell: jest.fn(() => ({
+                innerHTML: "",
+                style: {},
+                onmouseover: jest.fn(),
+                onmouseout: jest.fn()
+            })),
+            append: jest.fn()
+        }));
+        document.querySelectorAll = jest.fn(() => [
+            { style: {} },
+            { style: {} },
+            { style: {} },
+            { style: {} },
+            { style: {} },
+            { style: {} },
+            { style: {} }
+        ]);
+
+        widget._graphOfNotes();
+
+        expect(widget.circleIsVisible).toBe(true);
+    });
+
+    test("_refreshInnerWheel updates temporary ratios", () => {
+        widget.frequencies = [440];
+        widget.tempRatios1 = [1];
+        widget.tempRatios = [1];
+
+        global.docById = jest.fn(id => {
+            if (id === "frequencySlider") {
+                return { value: 880 };
+            }
+            if (id === "frequencydiv") {
+                return { innerHTML: "" };
+            }
+            return {
+                style: {},
+                innerHTML: ""
+            };
+        });
+
+        widget._logo = {
+            resetSynth: jest.fn(),
+            synth: { trigger: jest.fn() }
+        };
+
+        widget._createInnerWheel = jest.fn();
+
+        widget._refreshInnerWheel();
+
+        expect(widget._createInnerWheel).toHaveBeenCalled();
+    });
+
+    test("octaveSpaceEdit handles non-2 ratio", () => {
+        widget.ratios = [1, 2];
+        widget.frequencies = [440, 880];
+        widget.powerBase = 2;
+        widget.pitchNumber = 1;
+
+        widget.activity = {
+            textMsg: jest.fn()
+        };
+
+        global.docById = jest.fn(id => {
+            if (id === "startNote") return { value: 3 };
+            if (id === "endNote") return { value: 1 };
+            return {
+                innerHTML: "",
+                style: {},
+                append: jest.fn()
+            };
+        });
+
+        widget.checkTemperament = jest.fn();
+        widget._circleOfNotes = jest.fn();
+
+        widget.octaveSpaceEdit();
+
+        expect(widget.editMode).toBe("octave");
+    });
+
+    test("playAll handles reverse playback", () => {
+        widget._logo = {
+            resetSynth: jest.fn(),
+            synth: {
+                trigger: jest.fn(),
+                stop: jest.fn(),
+                setMasterVolume: jest.fn(),
+                startingPitch: "C4"
+            }
+        };
+
+        widget.playButton = { innerHTML: "" };
+        widget.pitchNumber = 1;
+        widget.frequencies = [440, 880];
+        widget.tempRatios1 = [1, 2];
+        widget.circleIsVisible = false;
+        widget.notesCircle = {
+            navItems: [
+                { fillAttr: "", sliceHoverAttr: {}, slicePathAttr: {}, sliceSelectedAttr: {} },
+                { fillAttr: "", sliceHoverAttr: {}, slicePathAttr: {}, sliceSelectedAttr: {} }
+            ],
+            refreshWheel: jest.fn()
+        };
+
+        global.docById = jest.fn(() => null);
+
+        widget.playAll();
+
+        expect(widget._playing).toBe(true);
+    });
+
+    test("playAll stops when already playing", () => {
+        widget._logo = {
+            resetSynth: jest.fn(),
+            synth: {
+                stop: jest.fn(),
+                setMasterVolume: jest.fn(),
+                startingPitch: "C4" // 👈 REQUIRED
+            }
+        };
+
+        widget.playButton = { innerHTML: "" };
+        widget._playing = true;
+        widget.tempRatios1 = [1];
+
+        widget.playAll();
+
+        expect(widget._playing).toBe(false);
+    });
+
+    test("_save executes without crash", () => {
+        global.setOctaveRatio = jest.fn();
+        global.rationalToFraction = jest.fn(() => [1, 1]);
+        global.getOctaveRatio = jest.fn(() => 2);
+
+        widget.inTemperament = "equal";
+        widget.ratios = [1, 2];
+        widget.notes = [
+            ["C", 4],
+            ["C", 5]
+        ];
+        widget.powerBase = 2;
+
+        widget._logo = {
+            synth: {
+                stop: jest.fn(),
+                startingPitch: "C4"
+            }
+        };
+
+        widget.activity = {
+            blocks: {
+                loadNewBlocks: jest.fn(),
+                findUniqueTemperamentName: jest.fn(() => "custom1")
+            }
+        };
+
+        widget._save();
+
+        expect(widget.activity.blocks.loadNewBlocks).toHaveBeenCalled();
+    });
+});
diff --git a/js/widgets/temperament.js b/js/widgets/temperament.js
index d69a201527..51d3f6c270 100644
--- a/js/widgets/temperament.js
+++ b/js/widgets/temperament.js
@@ -2195,7 +2195,9 @@ function TemperamentWidget() {
         row.id = "buttonsRow";
 
         temperamentCell = row.insertCell();
-        temperamentCell.innerHTML = this.inTemperament;
+        if (temperamentCell) {
+            temperamentCell.innerHTML = this.inTemperament;
+        }
         temperamentCell.style.width = 2 * BUTTONSIZE + "px";
         temperamentCell.style.minWidth = temperamentCell.style.width;
         temperamentCell.style.maxWidth = temperamentCell.style.width;
@@ -2332,3 +2334,7 @@ function TemperamentWidget() {
         widgetWindow.sendToCenter();
     };
 }
+
+if (typeof module !== "undefined") {
+    module.exports = TemperamentWidget;
+}