diff --git a/src/components/menu/menu.test.ts b/src/components/menu/menu.test.ts
index 27f01869..0c901356 100644
--- a/src/components/menu/menu.test.ts
+++ b/src/components/menu/menu.test.ts
@@ -37,7 +37,7 @@ const expectSelectHandlerToHaveBeenCalledOn = async (
   selectHandler: sinon.SinonSpy,
   expectedValue: string
 ): Promise<void> => {
-  await waitUntil(() => selectHandler.calledOnce);
+  await waitUntil(() => selectHandler.called);
   expect(selectHandler).to.have.been.calledOnce;
   const event = selectHandler.args[0][0] as CustomEvent;
   const detail = event.detail as Payload;
diff --git a/src/components/relative-time/relative-time.test.ts b/src/components/relative-time/relative-time.test.ts
new file mode 100644
index 00000000..bcca2469
--- /dev/null
+++ b/src/components/relative-time/relative-time.test.ts
@@ -0,0 +1,201 @@
+import { expect, fixture, html } from '@open-wc/testing';
+import { LocalizeController } from '@shoelace-style/localize';
+import sinon from 'sinon';
+import type SlRelativeTime from './relative-time';
+
+interface SlRelativeTimeTestCase {
+  date: Date;
+  expectedOutput: string;
+}
+
+const extractTimeElement = (relativeTime: SlRelativeTime): HTMLTimeElement | null => {
+  return relativeTime.shadowRoot?.querySelector('time') || null;
+};
+
+const expectFormattedRelativeTimeToBe = async (relativeTime: SlRelativeTime, expectedOutput: string): Promise<void> => {
+  await relativeTime.updateComplete;
+  const textContent = extractTimeElement(relativeTime)?.textContent;
+  expect(textContent).to.equal(expectedOutput);
+};
+
+const createRelativeTimeWithDate = async (relativeDate: Date): Promise<SlRelativeTime> => {
+  const relativeTime: SlRelativeTime = await fixture<SlRelativeTime>(
+    html` <sl-relative-time lang="en-US"></sl-relative-time> `
+  );
+  relativeTime.date = relativeDate;
+  return relativeTime;
+};
+
+const expectTitleToMatchLocalizedTimeString = (relativeTime: SlRelativeTime) => {
+  const localize = new LocalizeController(relativeTime);
+  const titleTime = localize.date(yesterday, {
+    month: 'long',
+    year: 'numeric',
+    day: 'numeric',
+    hour: 'numeric',
+    minute: 'numeric',
+    timeZoneName: 'short'
+  });
+  const timeElement = extractTimeElement(relativeTime);
+  expect(timeElement?.title).to.equal(titleTime);
+};
+
+const minuteInSeconds = 60_000;
+const hourInSeconds = minuteInSeconds * 60;
+const dayInSeconds = hourInSeconds * 24;
+const weekInSeconds = dayInSeconds * 7;
+const monthInSeconds = dayInSeconds * 30;
+const nonLeapYearInSeconds = dayInSeconds * 356;
+
+const currentTime = new Date('2022-10-30T15:22:10.100Z');
+const yesterday = new Date(currentTime.getTime() - dayInSeconds);
+const testCases: SlRelativeTimeTestCase[] = [
+  {
+    date: new Date(currentTime.getTime() - minuteInSeconds),
+    expectedOutput: '1 minute ago'
+  },
+  {
+    date: new Date(currentTime.getTime() - hourInSeconds),
+    expectedOutput: '1 hour ago'
+  },
+  {
+    date: yesterday,
+    expectedOutput: 'yesterday'
+  },
+  {
+    date: new Date(currentTime.getTime() - 4 * dayInSeconds),
+    expectedOutput: '4 days ago'
+  },
+  {
+    date: new Date(currentTime.getTime() - weekInSeconds),
+    expectedOutput: 'last week'
+  },
+  {
+    date: new Date(currentTime.getTime() - monthInSeconds),
+    expectedOutput: 'last month'
+  },
+  {
+    date: new Date(currentTime.getTime() - nonLeapYearInSeconds),
+    expectedOutput: 'last year'
+  },
+  {
+    date: new Date(currentTime.getTime() + minuteInSeconds),
+    expectedOutput: 'in 1 minute'
+  }
+];
+
+describe('sl-relative-time', () => {
+  it('should pass accessibility tests', async () => {
+    const relativeTime = await createRelativeTimeWithDate(currentTime);
+
+    await expect(relativeTime).to.be.accessible();
+  });
+
+  describe('handles time correctly', () => {
+    let clock: sinon.SinonFakeTimers | null = null;
+
+    beforeEach(() => {
+      clock = sinon.useFakeTimers(currentTime);
+    });
+
+    afterEach(() => {
+      clock?.restore();
+    });
+
+    testCases.forEach(testCase => {
+      it(`shows the correct relative time given a Date object: ${testCase.expectedOutput}`, async () => {
+        const relativeTime = await createRelativeTimeWithDate(testCase.date);
+
+        await expectFormattedRelativeTimeToBe(relativeTime, testCase.expectedOutput);
+      });
+
+      it(`shows the correct relative time given a String object: ${testCase.expectedOutput}`, async () => {
+        const dateString = testCase.date.toISOString();
+
+        const relativeTime: SlRelativeTime = await fixture<SlRelativeTime>(
+          html` <sl-relative-time lang="en-US" date="${dateString}"></sl-relative-time> `
+        );
+
+        await expectFormattedRelativeTimeToBe(relativeTime, testCase.expectedOutput);
+      });
+    });
+
+    it('always shows numeric if requested via numeric property', async () => {
+      const relativeTime: SlRelativeTime = await fixture<SlRelativeTime>(
+        html` <sl-relative-time lang="en-US" numeric="always"></sl-relative-time> `
+      );
+      relativeTime.date = yesterday;
+
+      await expectFormattedRelativeTimeToBe(relativeTime, '1 day ago');
+    });
+
+    it('shows human readable form if appropriate and numeric property is auto', async () => {
+      const relativeTime: SlRelativeTime = await fixture<SlRelativeTime>(
+        html` <sl-relative-time lang="en-US" numeric="auto"></sl-relative-time> `
+      );
+      relativeTime.date = yesterday;
+
+      await expectFormattedRelativeTimeToBe(relativeTime, 'yesterday');
+    });
+
+    it('shows the set date with the proper attributes at the time object', async () => {
+      const relativeTime = await createRelativeTimeWithDate(yesterday);
+
+      await relativeTime.updateComplete;
+      const timeElement = extractTimeElement(relativeTime);
+      expect(timeElement?.dateTime).to.equal(yesterday.toISOString());
+      expectTitleToMatchLocalizedTimeString(relativeTime);
+    });
+
+    it('allows to use a short form of the unit', async () => {
+      const twoYearsAgo = new Date(currentTime.getTime() - 2 * nonLeapYearInSeconds);
+      const relativeTime: SlRelativeTime = await fixture<SlRelativeTime>(
+        html` <sl-relative-time lang="en-US" numeric="always" format="short"></sl-relative-time> `
+      );
+      relativeTime.date = twoYearsAgo;
+
+      await expectFormattedRelativeTimeToBe(relativeTime, '2 yr. ago');
+    });
+
+    it('allows to use a long form of the unit', async () => {
+      const twoYearsAgo = new Date(currentTime.getTime() - 2 * nonLeapYearInSeconds);
+      const relativeTime: SlRelativeTime = await fixture<SlRelativeTime>(
+        html` <sl-relative-time lang="en-US" numeric="always" format="long"></sl-relative-time> `
+      );
+      relativeTime.date = twoYearsAgo;
+
+      await expectFormattedRelativeTimeToBe(relativeTime, '2 years ago');
+    });
+
+    it('is formatted according to the requested locale', async () => {
+      const relativeTime: SlRelativeTime = await fixture<SlRelativeTime>(
+        html` <sl-relative-time lang="de-DE" numeric="auto"></sl-relative-time> `
+      );
+      relativeTime.date = yesterday;
+
+      await expectFormattedRelativeTimeToBe(relativeTime, 'gestern');
+    });
+
+    it('keeps the component in sync if requested', async () => {
+      const relativeTime = await createRelativeTimeWithDate(yesterday);
+      relativeTime.sync = true;
+
+      await expectFormattedRelativeTimeToBe(relativeTime, 'yesterday');
+
+      clock?.tick(dayInSeconds);
+
+      await expectFormattedRelativeTimeToBe(relativeTime, '2 days ago');
+    });
+  });
+
+  it('does not display a time element on invalid time string', async () => {
+    const invalidDateString = 'thisIsNotATimeString';
+
+    const relativeTime: SlRelativeTime = await fixture<SlRelativeTime>(
+      html` <sl-relative-time lang="en-US" date="${invalidDateString}"></sl-relative-time> `
+    );
+
+    await relativeTime.updateComplete;
+    expect(extractTimeElement(relativeTime)).to.be.null;
+  });
+});