diff --git a/src/lib/tauriEnv.test.ts b/src/lib/tauriEnv.test.ts
new file mode 100644
index 0000000..bfb6267
--- /dev/null
+++ b/src/lib/tauriEnv.test.ts
@@ -0,0 +1,120 @@
+import { afterEach, describe, expect, it } from "vitest";
+import { isTauriRuntime } from "./tauriEnv";
+
+type MarkerKey = "__TAURI_INTERNALS__" | "__TAURI__" | "isTauri";
+
+const MARKERS: MarkerKey[] = ["__TAURI_INTERNALS__", "__TAURI__", "isTauri"];
+
+const initialWindow = Object.getOwnPropertyDescriptor(globalThis, "window");
+const baselineRuntime = isTauriRuntime();
+
+function restoreWindow(): void {
+  if (initialWindow) {
+    Object.defineProperty(globalThis, "window", initialWindow);
+    return;
+  }
+  Reflect.deleteProperty(globalThis, "window");
+}
+
+function installWindow(markers: Partial<Record<MarkerKey, unknown>> = {}): void {
+  const next: Record<string, unknown> = {};
+  for (const key of MARKERS) {
+    if (Object.prototype.hasOwnProperty.call(markers, key)) {
+      next[key] = markers[key];
+    }
+  }
+  Object.defineProperty(globalThis, "window", {
+    configurable: true,
+    enumerable: true,
+    writable: true,
+    value: next,
+  });
+}
+
+function removeWindow(): void {
+  Reflect.deleteProperty(globalThis, "window");
+}
+
+afterEach(() => {
+  restoreWindow();
+});
+
+describe("isTauriRuntime", () => {
+  it("isTauriRuntime_false_when_window_unavailable", () => {
+    try {
+      removeWindow();
+      expect(isTauriRuntime()).toBe(false);
+    } finally {
+      restoreWindow();
+    }
+  });
+
+  it("isTauriRuntime_false_when_browser_window_has_no_markers", () => {
+    try {
+      installWindow();
+      expect(isTauriRuntime()).toBe(false);
+    } finally {
+      restoreWindow();
+    }
+  });
+
+  it("isTauriRuntime_true_for___TAURI_INTERNALS___alone", () => {
+    try {
+      installWindow({ __TAURI_INTERNALS__: {} });
+      expect(isTauriRuntime()).toBe(true);
+    } finally {
+      restoreWindow();
+    }
+  });
+
+  it("isTauriRuntime_true_for___TAURI___alone", () => {
+    try {
+      installWindow({ __TAURI__: {} });
+      expect(isTauriRuntime()).toBe(true);
+    } finally {
+      restoreWindow();
+    }
+  });
+
+  it("isTauriRuntime_true_for_isTauri_alone", () => {
+    try {
+      installWindow({ isTauri: true });
+      expect(isTauriRuntime()).toBe(true);
+    } finally {
+      restoreWindow();
+    }
+  });
+
+  it("isTauriRuntime_falsey_markers_are_not_a_runtime", () => {
+    try {
+      const falseyValues: unknown[] = [false, 0, "", null, undefined];
+      for (const value of falseyValues) {
+        installWindow({
+          __TAURI_INTERNALS__: value,
+          __TAURI__: value,
+          isTauri: value,
+        });
+        expect(isTauriRuntime()).toBe(false);
+      }
+      for (const key of MARKERS) {
+        installWindow({ [key]: false } as Partial<Record<MarkerKey, unknown>>);
+        expect(isTauriRuntime()).toBe(false);
+      }
+    } finally {
+      restoreWindow();
+    }
+  });
+
+  it("isTauriRuntime_restores_global_window_markers", () => {
+    try {
+      installWindow({ __TAURI_INTERNALS__: {}, __TAURI__: {}, isTauri: true });
+      expect(isTauriRuntime()).toBe(true);
+    } finally {
+      restoreWindow();
+    }
+    expect(Object.getOwnPropertyDescriptor(globalThis, "window")).toEqual(
+      initialWindow,
+    );
+    expect(isTauriRuntime()).toBe(baselineRuntime);
+  });
+});