diff --git a/test/utils/TestAsync.ts b/test/utils/TestAsync.ts
new file mode 100644
index 0000000..9737282
--- /dev/null
+++ b/test/utils/TestAsync.ts
@@ -0,0 +1,15 @@
+import { expect } from 'chai';
+
+import { defer, timeout } from '../../src/utils/Async';
+import { describeLeaks, itLeaks } from '../helpers/async';
+import { TimeoutError } from '../../src';
+
+describeLeaks('async utils', async () => {
+  describeLeaks('defer', async () => {
+    itLeaks('should resolve', async () => expect(defer(10, true)).to.eventually.equal(true));
+  });
+
+  describeLeaks('timeout', async () => {
+    itLeaks('should reject slow promises', async () => expect(timeout(10, defer(20))).to.eventually.be.rejectedWith(TimeoutError));
+  });
+});
diff --git a/test/utils/TestBuffer.ts b/test/utils/TestBuffer.ts
new file mode 100644
index 0000000..8658681
--- /dev/null
+++ b/test/utils/TestBuffer.ts
@@ -0,0 +1,33 @@
+import { expect } from 'chai';
+
+import { concat, encode } from '../../src/utils/Buffer';
+import { describeLeaks, itLeaks } from '../helpers/async';
+
+describeLeaks('buffer utils', async () => {
+  describeLeaks('concat', async () => {
+    itLeaks('should append chunk buffers', async () => {
+      expect(concat([
+        Buffer.from('hello'),
+        Buffer.from('world'),
+      ])).to.deep.equal(Buffer.from('helloworld'));
+    });
+  });
+
+  describeLeaks('encode', async () => {
+    itLeaks('should encode chunk buffers', async () => {
+      expect(encode([
+        Buffer.from('hello world'),
+      ], 'utf-8')).to.equal('hello world');
+    });
+
+    itLeaks('should encode no buffers', async () => {
+      expect(encode([], 'utf-8')).to.equal('');
+    });
+
+    itLeaks('should encode empty buffers', async () => {
+      expect(encode([
+        new Buffer(0),
+      ], 'utf-8')).to.equal('');
+    });
+  });
+});
diff --git a/test/utils/TestMap.ts b/test/utils/TestMap.ts
index 0876230..b7caa23 100644
--- a/test/utils/TestMap.ts
+++ b/test/utils/TestMap.ts
@@ -10,6 +10,9 @@ import {
   makeMap,
   mustGet,
   pairsToMap,
+  setOrPush,
+  mergeMap,
+  pushMergeMap,
 } from '../../src/utils/Map';
 import { describeLeaks, itLeaks } from '../helpers/async';
 
@@ -102,7 +105,10 @@ describeLeaks('map utils', async () => {
       expect(getOrDefault(singleItem, 'missing', DEFAULT_VALUE)).to.equal(DEFAULT_VALUE);
     });
 
-    xit('should return the default for nil values');
+    it('should return the default for nil values', () => {
+      expect(getOrDefault(multiItem, 'nilKey', DEFAULT_VALUE)).to.equal(DEFAULT_VALUE);
+    });
+
     xit('should return falsy values for existing keys');
   });
 
@@ -140,4 +146,64 @@ describeLeaks('map utils', async () => {
       expect(entriesOf(undefined)).to.deep.equal([]);
     });
   });
+
+  describe('set or push helper', () => {
+    xit('should insert new lists');
+
+    it('should wrap new items', () => {
+      const values = new Map<string, Array<string>>([]);
+      setOrPush(values, mapKey, 'fin');
+
+      expect(Array.from(values.keys()).length).to.equal(1);
+      expect(mustGet(values, mapKey).length).to.equal(1);
+    });
+
+    it('should append to existing items', () => {
+      const values = new Map(multiItem);
+      setOrPush(values, mapKey, 'fin');
+
+      expect(Array.from(values.keys()).length).to.equal(3);
+      expect(mustGet(values, mapKey).length).to.equal(2);
+    });
+  });
+
+  describe('merge map helper', () => {
+    it('should combine two maps', () => {
+      const firstValue = new Map([[mapKey, mapValue]]);
+      const otherValue = new Map([['foo', 'bar']]);
+
+      const merged = mergeMap(firstValue, otherValue);
+
+      expect(Array.from(merged.keys()).length).to.equal(2);
+    });
+  });
+
+  describe('push merge map helper', () => {
+    it('should combine two overlapping maps', () => {
+      const firstValue = new Map([[mapKey, [1]]]);
+      const otherValue = new Map([[mapKey, [2, 3]]]);
+
+      const merged = pushMergeMap(firstValue, otherValue);
+      expect(merged).to.have.keys(mapKey);
+      expect(merged.get(mapKey)).to.deep.equal([1, 2, 3]);
+    });
+  });
+
+  describe('make map helper', () => {
+    it('should make an empty map', () => {
+      expect(makeMap(undefined).size).to.equal(0);
+    });
+
+    it('should copy an existing map', () => {
+      const copy = makeMap(singleItem);
+      expect(copy).to.deep.equal(singleItem);
+      expect(copy).not.to.equal(singleItem);
+    });
+
+    it('should copy a dict', () => {
+      expect(makeMap({
+        [mapKey]: mapValue,
+      })).to.deep.equal(singleItem);
+    });
+  });
 });
diff --git a/test/utils/TestReflect.ts b/test/utils/TestReflect.ts
new file mode 100644
index 0000000..7897df4
--- /dev/null
+++ b/test/utils/TestReflect.ts
@@ -0,0 +1,18 @@
+import { expect } from 'chai';
+import { getMethods } from '../../src/utils/Reflect';
+
+describe('reflect utils', () => {
+  describe('get methods helper', () => {
+    it('should collect method functions', () => {
+      class Test {
+        public foo() { /* noop */ }
+        public bar() { /* noop */ }
+      }
+
+      const methods = getMethods(new Test()).values();
+      /* eslint-disable @typescript-eslint/unbound-method */
+      expect(methods).to.include(Test.prototype.foo);
+      expect(methods).to.include(Test.prototype.bar);
+    });
+  });
+});