diff --git a/test/util/npmrc.spec.ts b/test/util/npmrc.spec.ts
index 7b93321..77d2a7d 100644
--- a/test/util/npmrc.spec.ts
+++ b/test/util/npmrc.spec.ts
@@ -27,5 +27,11 @@ describe('npmrc', () => {
       expect(registry).toMatch(RE_URL);
       expect(otherRegistries).toHaveLength(0);
     });
+
+    it('should not throw when an undefined value is passed in', () => {
+      const registry = getRegistryFromNpmrc();
+
+      expect(registry).toEqual([]);
+    });
   });
 });
diff --git a/test/util/string.spec.ts b/test/util/string.spec.ts
new file mode 100644
index 0000000..0cf4be3
--- /dev/null
+++ b/test/util/string.spec.ts
@@ -0,0 +1,17 @@
+import { removeTrailingSlash } from '../../src/util/string';
+
+describe('string', () => {
+  describe('removeTrailingSlash', () => {
+    it('should remove trailing slashes with expected inputs', () => {
+      expect(removeTrailingSlash('https://google.com/')).toEqual(
+        'https://google.com'
+      );
+
+      expect(removeTrailingSlash(0)).toEqual('');
+
+      expect(
+        removeTrailingSlash('http://local/url/with/trailing/slash/')
+      ).toEqual('http://local/url/with/trailing/slash');
+    });
+  });
+});