diff --git a/src/randomstring.ts b/src/randomstring.ts
index 3362c0b02..0ed46fb38 100644
--- a/src/randomstring.ts
+++ b/src/randomstring.ts
@@ -15,9 +15,24 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
+const LOWERCASE = "abcdefghijklmnopqrstuvwxyz";
+const UPPERCASE = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
+const DIGITS = "0123456789";
+
 export function randomString(len: number): string {
+    return randomStringFrom(len, UPPERCASE + LOWERCASE + DIGITS);
+}
+
+export function randomLowercaseString(len: number): string {
+    return randomStringFrom(len, LOWERCASE);
+}
+
+export function randomUppercaseString(len: number): string {
+    return randomStringFrom(len, UPPERCASE);
+}
+
+function randomStringFrom(len: number, chars: string): string {
     let ret = "";
-    const chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
 
     for (let i = 0; i < len; ++i) {
         ret += chars.charAt(Math.floor(Math.random() * chars.length));