Support .'s in prerelease versions when testing

Author: pimterry

test/integration-test.spec.ts

@@ -20,9 +20,9 @@ async function setupServerPath() {
 
     // If TEST_BUILT_TARBALL is set, test the latest built ready-to-go tarball:
     const tmpDir = tmp.dirSync({ unsafeCleanup: true }).name;
-    const version = require(path.join('..', 'package.json')).version;
+    const version: string = require(path.join('..', 'package.json')).version;
 
-    const channel = version.split('-')[1] || '';
+    const channel = (version.split('-')[1] || '').split('.')[0];
 
     const tarballPath = path.join(
         __dirname,