Reorganize test cases

ts/test-node/util/isNormalNumber_test.ts

@@ -0,0 +1,45 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { assert } from 'chai';
+
+import { isNormalNumber } from '../../util/isNormalNumber';
+
+describe('isNormalNumber', () => {
+  it('returns false for non-numbers', () => {
+    assert.isFalse(isNormalNumber(undefined));
+    assert.isFalse(isNormalNumber(null));
+    assert.isFalse(isNormalNumber('123'));
+    assert.isFalse(isNormalNumber(BigInt(123)));
+  });
+
+  it('returns false for Number objects, which should never be used', () => {
+    // eslint-disable-next-line no-new-wrappers
+    assert.isFalse(isNormalNumber(new Number(123)));
+  });
+
+  it('returns false for values that can be converted to numbers', () => {
+    const obj = {
+      [Symbol.toPrimitive]() {
+        return 123;
+      },
+    };
+    assert.isFalse(isNormalNumber(obj));
+  });
+
+  it('returns false for NaN', () => {
+    assert.isFalse(isNormalNumber(NaN));
+  });
+
+  it('returns false for Infinity', () => {
+    assert.isFalse(isNormalNumber(Infinity));
+    assert.isFalse(isNormalNumber(-Infinity));
+  });
+
+  it('returns true for other numbers', () => {
+    assert.isTrue(isNormalNumber(123));
+    assert.isTrue(isNormalNumber(0));
+    assert.isTrue(isNormalNumber(-1));
+    assert.isTrue(isNormalNumber(0.12));
+  });
+});