test: add tests for get-used-version task

src/tasks/get-used-version.ts

@@ -53,6 +53,7 @@ export async function getUsedVersion(path: PathLike, dependency: string): Promis
 export async function getUsedVersionMajorMinor(path: PathLike, dependency: string): Promise<string> {
   const versionMatch = (await getUsedVersion(path, dependency)).match(/([0-9]+\.[0-9]+)\.[0-9]+/);
 
+  // istanbul ignore if
   if (versionMatch === null) {
     throw new Error(`Used version of '${dependency}' of project in '${path}' could not be determined.`);
   }