Custom configuration in gradle - gradle

Question

I'm defining separate configuration in gradle for jupiter (Junit 5) tests. I have following snippet in the gradle file:
My understanding is jupiterCompile will extend dependencies from testCompile including any dependencies defined for self. In this case my testCompile configuration doesn't have any jupiter dependencies but as jupiterCompile has those sets of dependencies, I expect them to be available. However, if I write testCompile.extendsFrom jupiterCompile it does work which is confusing to me.
configurations {
jupiterTestCompile.extendsFrom testCompile
jupiterTestRuntime.extendsFrom testRuntime
jupiterTestCompileOnly.extendsFrom testCompileOnly
}
dependencies {
def jUnitVersion = "5.5.1"
jupiterTestCompile("org.junit.jupiter:junit-jupiter-
api:${jUnitVersion}")
jupiterTestRuntime("org.junit.jupiter:junit-jupiter-
engine:${jUnitVersion}")
jupiterTestCompileOnly("org.junit.jupiter:junit-jupiter-
migrationsupport:${jUnitVersion}")
jupiterTestRuntime("org.junit.vintage:junit-vintage-
engine:${jUnitVersion}")
}
If I have common dependencies defined under testCompile and want jupiterCompile configuration to inherit them, what should be the right configuration?