Timeline: repair oldest/newest metrics if we fetch nothing

ts/test-node/linkPreviews/isLinkPreviewDateValid_test.ts

@@ -0,0 +1,44 @@
+// Copyright 2020 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { assert } from 'chai';
+
+import { isLinkPreviewDateValid } from '../../linkPreviews/isLinkPreviewDateValid';
+
+describe('isLinkPreviewDateValid', () => {
+  it('returns false for non-numbers', () => {
+    assert.isFalse(isLinkPreviewDateValid(null));
+    assert.isFalse(isLinkPreviewDateValid(undefined));
+    assert.isFalse(isLinkPreviewDateValid(Date.now().toString()));
+    assert.isFalse(isLinkPreviewDateValid(new Date()));
+  });
+
+  it('returns false for zero', () => {
+    assert.isFalse(isLinkPreviewDateValid(0));
+    assert.isFalse(isLinkPreviewDateValid(-0));
+  });
+
+  it('returns false for NaN', () => {
+    assert.isFalse(isLinkPreviewDateValid(0 / 0));
+  });
+
+  it('returns false for any infinite value', () => {
+    assert.isFalse(isLinkPreviewDateValid(Infinity));
+    assert.isFalse(isLinkPreviewDateValid(-Infinity));
+  });
+
+  it('returns false for timestamps more than a day from now', () => {
+    const twoDays = 2 * 24 * 60 * 60 * 1000;
+    assert.isFalse(isLinkPreviewDateValid(Date.now() + twoDays));
+  });
+
+  it('returns true for timestamps before tomorrow', () => {
+    assert.isTrue(isLinkPreviewDateValid(Date.now()));
+    assert.isTrue(isLinkPreviewDateValid(Date.now() + 123));
+    assert.isTrue(isLinkPreviewDateValid(Date.now() - 123));
+    assert.isTrue(isLinkPreviewDateValid(new Date(1995, 3, 20).valueOf()));
+    assert.isTrue(isLinkPreviewDateValid(new Date(1970, 3, 20).valueOf()));
+    assert.isTrue(isLinkPreviewDateValid(new Date(1969, 3, 20).valueOf()));
+    assert.isTrue(isLinkPreviewDateValid(1));
+  });
+});