build.gradle fix tests

app/build.gradle

@@ -11,8 +11,6 @@ plugins {
     id 'application'
 }
 
-project.ext.os = System.properties['os.name'].toLowerCase().split(" ")[0]
-
 repositories {
     // Use Maven Central for resolving dependencies.
     mavenCentral()
@@ -22,6 +20,8 @@ dependencies {
     // Use JUnit Jupiter for testing.
     testImplementation 'org.junit.jupiter:junit-jupiter:5.9.1'
 
+    implementation 'com.google.guava:guava:31.1-jre'
+
     implementation 'org.json:json:20250107'
 
     implementation "io.github.spair:imgui-java-app:1.88.0"
@@ -50,6 +50,10 @@ jar {
     } 
 }
 
+test {
+    useJUnitPlatform()
+}
+
 run {
     enableAssertions = true
 }