Reorganize test cases

ts/test-node/util/dropNull_test.ts

@@ -0,0 +1,62 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+import { assert } from 'chai';
+
+import { dropNull, shallowDropNull } from '../../util/dropNull';
+
+type Test = {
+  a: number | null;
+  b: number | undefined;
+};
+
+describe('dropNull', () => {
+  it('swaps null with undefined', () => {
+    assert.strictEqual(dropNull(null), undefined);
+  });
+
+  it('leaves undefined be', () => {
+    assert.strictEqual(dropNull(undefined), undefined);
+  });
+
+  it('non-null values undefined be', () => {
+    assert.strictEqual(dropNull('test'), 'test');
+  });
+
+  describe('shallowDropNull', () => {
+    it('return undefined with given null', () => {
+      assert.strictEqual(shallowDropNull<Test>(null), undefined);
+    });
+
+    it('return undefined with given undefined', () => {
+      assert.strictEqual(shallowDropNull<Test>(undefined), undefined);
+    });
+
+    it('swaps null with undefined', () => {
+      const result:
+        | {
+            a: number | undefined;
+            b: number | undefined;
+          }
+        | undefined = shallowDropNull<Test>({
+        a: null,
+        b: 1,
+      });
+
+      assert.deepStrictEqual(result, { a: undefined, b: 1 });
+    });
+
+    it('leaves undefined be', () => {
+      const result:
+        | {
+            a: number | undefined;
+            b: number | undefined;
+          }
+        | undefined = shallowDropNull<Test>({
+        a: 1,
+        b: undefined,
+      });
+
+      assert.deepStrictEqual(result, { a: 1, b: undefined });
+    });
+  });
+});