gradle: switching to implementation/testImplementation causing errors when accessing configuration

I have a project which was building fine when I was using the depricated compile and testCompile, but when I switch it to implementation and testImplementation, this reference breaks.

def jmockit = configurations.testCompile.files.find { it.name.contains("jmockit") }.absolutePath

It gives the error Cannot get property 'absolutePath' on null object

When I try to change it like so

def jmockit = configurations.testImplementation.files.find { it.name.contains("jmockit") }.absolutePath

I get the error

Resolving configuration 'testImplementation' directly is not allowed

Based on other related questions, I've tried

def jmockit = configurations.compileClasspath.files.find { it.name.contains("jmockit") }.absolutePath

which again gives the Cannot get property 'absolutePath' on null object error.

What configuration are testImplementation dependencies going into? How do I access them in this way?

not sure if it's relevant but this is a java project in IntelliJ.

It breaks because testCompile does not extend from testImplementation. In fact it's the other way around.

You can see the full test configuration hierarchy in Figure 3. Java plugin - test source set dependency configurations from
Dependency configurations docs.

You must use the testCompileClasspath to retrieve the absolutePath you seek. Full example below (Kotlin DSL):

plugins {
    id("java")
}

repositories {
    mavenCentral()
}

group = "io.mateo.test"

dependencies {
    testImplementation("org.apache.commons:commons-lang3:3.11")
    testImplementation("org.jmockit:jmockit:1.49")
}

val jmockit = configurations.testCompileClasspath.get().files.filter { it.name.contains("jmockit") }[0]

println(jmockit.absoluteFile)

With the above, you will see the path you're after:

$ ./gradlew assemble

> Configure project :
C:\Users\fmate\.gradle\caches\modules-2\files-2.1\org.jmockit\jmockit.49\e281fc6778c43060402505f062f6515c2adeb037\jmockit-1.49.jar

BUILD SUCCESSFUL in 731ms
2 actionable tasks: 2 up-to-date