This message was deleted.

You need too add all "peer" dependencies to the pluginClasspath to have them in the right class loader. Something like:

val additionalPluginClasspath by configurations.creating

dependencies {
    additionalPluginClasspath("com.google.cloud.tools.jib:com.google.cloud.tools.jib.gradle.plugin:3.3.0")
}

tasks {
    pluginUnderTestMetadata {
        this.pluginClasspath.from(additionalPluginClasspath)
    }
}

and then use it without version from your test project:

plugins {
    id("com.google.cloud.tools.jib")
}

umm ok, I forgot to mention that I'm declaring Jib as an

implementation

dependency of my plugin, assuming it'll get applied automatically and also loaded at test time. Does that count or am I taking the wrong assumption and doing it wrong? The official docs didn't help much in this regard

Oh, if declared as

implementation

then

additionalPluginClasspath

shouldn't be needed.

also, as I said I didn't experience any error running the exact same build from the CLI using an actual Gradle daemon