cannot find symbol intellij gradle

This seemingly very simple or even silly question has been bothering me.

What I did:

1. On my fresh new Mac OS X 10.13.6

2. I used Intellij CE 2018.1 version to check out a repo from Github.

3. Whenever I tried to run unit tests in this repo from my Intellij, it simply says: "Cannot find symbol", screenshot below:

4. I didn't make any changes locally, this is a build green project that I checked out from a git repo.

5. this is build.gradle file

   apply plugin: 'java' apply plugin: 'checkstyle' group = 'com.fishercoder' version = '1.0-SNAPSHOT' checkstyle { //include ( '**/*.java') configFile = file("${rootDir}/fishercoder_checkstyle.xml") } description = """""" sourceCompatibility = 1.9 targetCompatibility = 1.9 repositories { mavenCentral() maven { url "http://repo.maven.apache.org/maven2" } } dependencies { compile 'com.google.code.gson:gson:2.8.0' testCompile group: 'junit', name: 'junit', version:'4.12' } 

What I've tried:

1. Interestingly, I could print out a "Hello world" in src code part, but tst part just don't compile in Intellij.
2. I've invalidated caches and restart my Intelij, no luck.
3. I've removed the folder on my disk, completely shutdown my Intellij, redo git clone into my disk first, then open Intellij to import it, see below:

Then imported it as a gradle project, see below:

Left everything on the following page as default:

Then in my Intellij console, I got this error: Any help is appreciated!