test: add tests for finding babel config file

Author: Robin-Hoodie

lib/build.spec.js

@@ -89,5 +89,44 @@ describe('build', () => {
         '.custom',
       ]);
     });
+
+    describe("babel config file resolution", () => {
+      const findBabelLoaderRule = rules => rules.find(rule => rule.use.loader.includes("babel-loader"));
+
+      it("should alter the default babelOpts when no valid babel config file is found", async () => {
+        setupFunction("", "not-babel.config.js");
+
+        const stats = await build.run(functions);
+        const babelLoaderRuleOptions = findBabelLoaderRule(stats.compilation.options.module.rules).use.options;
+
+        expect(babelLoaderRuleOptions.presets).toBeDefined();
+        expect(babelLoaderRuleOptions.plugins).toBeDefined();
+      });
+
+      it("should not alter the default babelOpts when a valid babel config file is found in same directory as the functions directory", async () => {
+        setupFunction("", "babel.config.js");
+
+        const stats = await build.run(functions);
+        const babelLoaderRuleOptions = findBabelLoaderRule(stats.compilation.options.module.rules).use.options;
+
+        expect(babelLoaderRuleOptions.presets).toBeUndefined();
+        expect(babelLoaderRuleOptions.plugins).toBeUndefined();
+      });
+
+      it("should not alter the default babelOpts when a valid babel config is found in directory above the functions directory", async () => {
+        setupFunction("", "babel.config.js");
+
+        const functionsSubDir = path.join(functions, "subdir");
+
+        fs.mkdirSync(functionsSubDir);
+        fs.writeFileSync(path.join(functionsSubDir, "index.js"), "");
+
+        const stats = await build.run(functionsSubDir);
+        const babelLoaderRuleOptions = findBabelLoaderRule(stats.compilation.options.module.rules).use.options;
+
+        expect(babelLoaderRuleOptions.presets).toBeUndefined();
+        expect(babelLoaderRuleOptions.plugins).toBeUndefined();
+      });
+    })
   });
 });