Add initial util test

src/util.test.ts

@@ -0,0 +1,9 @@
+import * as fs from 'fs';
+
+import * as util from './util';
+
+test('getToolNames', () => {
+  const input = fs.readFileSync(__dirname + '/testdata/tool-names.sarif', 'utf8')
+  const toolNames = util.getToolNames(input);
+  expect(toolNames).toStrictEqual(["CodeQL command-line toolchain", "ESLint"])
+})