fix: Add a test for the form reset feature fix.

Before modernization the reset button did not reset the placeholders in
the pat-content-mirror mirror element. Not it does. This test just shows it,
the fix was done in the previous commit.

Author: thet

src/pat-content-mirror.test.js

@@ -61,4 +61,62 @@ describe("pat-content-mirror", () => {
         expect(mirror2.textContent).toBe("this is a test text 2.");
     });
 
+    it("works with multiple content mirrors, placeholders and form resets.", async () => {
+        document.body.innerHTML = `
+            <form>
+                <p class="mirror-1">
+                    <span class="text">
+                        <em class="placeholder"></em>
+                    </span>
+                </p>
+                <textarea
+                    class="txt-1 pat-content-mirror"
+                    data-pat-content-mirror="target:.mirror-1 .text"
+                    placeholder="placeholder 1"></textarea>
+
+                <p class="mirror-2">
+                    <span class="text">
+                        <em class="placeholder"></em>
+                    </span>
+                </p>
+                <textarea
+                    class="txt-2 pat-content-mirror"
+                    data-pat-content-mirror="target:.mirror-2 .text"
+                    placeholder="placeholder 2"></textarea>
+
+                <button type="reset">Reset</button>
+            </form>
+        `;
+
+        const txt1 = document.querySelector(".txt-1");
+        const txt2 = document.querySelector(".txt-2");
+
+        const mirror1 = document.querySelector(".mirror-1 .text");
+        const mirror2 = document.querySelector(".mirror-2 .text");
+
+        const instance1 = new Pattern(txt1);
+        const instance2 = new Pattern(txt2);
+
+        await events.await_pattern_init(instance1);
+        await events.await_pattern_init(instance2);
+
+        expect(mirror1.textContent.trim()).toBe("placeholder 1");
+        expect(mirror2.textContent.trim()).toBe("placeholder 2");
+
+        txt1.value = "this is a test text 1.";
+        txt2.value = "this is a test text 2.";
+
+        txt1.dispatchEvent(new Event("input"));
+        txt2.dispatchEvent(new Event("input"));
+
+        expect(mirror1.textContent).toBe("this is a test text 1.");
+        expect(mirror2.textContent).toBe("this is a test text 2.");
+
+        const button = document.querySelector("button");
+        button.click();
+
+        expect(mirror1.textContent.trim()).toBe("placeholder 1");
+        expect(mirror2.textContent).toBe("placeholder 2");
+    });
+
 });