diff --git a/test/window_windows.c b/test/window_windows.c
new file mode 100644
index 00000000..0b4f1435
--- /dev/null
+++ b/test/window_windows.c
@@ -0,0 +1,80 @@
+// 24 may 2020
+#include "test_windows.h"
+
+Test(WindowHasHandleFromStart)
+{
+	uiWindow *a;
+
+	a = uiNewWindow();
+	if (uiWindowsControlHandle(uiControl(a)) == NULL)
+		TestErrorf("uiWindowsControlHandle(brand new uiWindow) is NULL; should not be");
+	uiControlFree(uiControl(a));
+}
+
+Test(InitialWindowTitleIsEmptyString_OSLevel)
+{
+	uiWindow *w;
+	HWND hwnd;
+	uint16_t *title;
+
+	w = uiNewWindow();
+	hwnd = uiWindowsControlHandle(uiControl(w));
+	title = testGetWindowText(hwnd);
+	if (!utf16equal(title, testUTF16Empty))
+		utf16diffError("brand new uiWindow has wrong title", title, testUTF16Empty);
+	free(title);
+	uiControlFree(uiControl(w));
+}
+
+static void testSetWindowTitleImplFull(const char *file, long line, const char *title, const uint16_t *want)
+{
+	uiWindow *w;
+	HWND hwnd;
+	uint16_t *got;
+
+	w = uiNewWindow();
+	uiWindowSetTitle(w, title);
+	hwnd = uiWindowsControlHandle(uiControl(w));
+	got = testGetWindowText(hwnd);
+	if (!utf16equal(got, want))
+		utf16diffErrorFull(file, line, "GetWindowTextW() reported wrong title after uiWindowSetTitle()", got, want);
+	free(got);
+	uiControlFree(uiControl(w));
+}
+
+#define testSetWindowTitleImpl(title, want) testSetWindowTitleImplFull(__FILE__, __LINE__, title, want)
+
+Test(SetWindowTitle_OSLevel_Empty)
+{
+	testSetWindowTitleImpl(testUTF8Empty, testUTF16Empty);
+}
+
+Test(SetWindowTitle_OSLevel_ASCIIOnly)
+{
+	testSetWindowTitleImpl(testUTF8ASCIIOnly, testUTF16ASCIIOnly);
+}
+
+Test(SetWindowTitle_OSLevel_WithTwoByte)
+{
+	testSetWindowTitleImpl(testUTF8WithTwoByte, testUTF16WithTwoByte);
+}
+
+Test(SetWindowTitle_OSLevel_WithThreeByte)
+{
+	testSetWindowTitleImpl(testUTF8WithThreeByte, testUTF16WithThreeByte);
+}
+
+Test(SetWindowTitle_OSLevel_WithFourByte)
+{
+	testSetWindowTitleImpl(testUTF8WithFourByte, testUTF16WithFourByte);
+}
+
+Test(SetWindowTitle_OSLevel_Combined)
+{
+	testSetWindowTitleImpl(testUTF8Combined, testUTF16Combined);
+}
+
+Test(SetWindowTitle_OSLevel_Invalid)
+{
+	testSetWindowTitleImpl(testUTF8InvalidInput, testUTF16InvalidOutput);
+}