Ensure LauncherConfigurationParametersTests runs in all environments

Prior to this commit, the warnsOnMultiplePropertyResources() test in
LauncherConfigurationParametersTests only ran within the Gradle build
or within IntelliJ IDEA when configured with "build" as the target
build directory.

However, other environments might not use a "build" directory. For
example, Eclipse uses a "bin" directory.

This commit therefore removes the hardcoded "build/resources/test" path
from the assertion and instead determines the URL for the resource by
loading it via the ClassLoader.

This commit also refactors the assertion to make it easier to follow.

Author: sbrannen

platform-tests/src/test/java/org/junit/platform/launcher/core/LauncherConfigurationParametersTests.java

@@ -10,6 +10,7 @@
 
 package org.junit.platform.launcher.core;
 
+import static org.assertj.core.api.Assertions.as;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertThrows;
@@ -18,12 +19,12 @@
 import java.net.URLClassLoader;
 import java.nio.file.Files;
 import java.nio.file.Path;
-import java.util.List;
 import java.util.Map;
 import java.util.Properties;
 import java.util.logging.Level;
 import java.util.logging.LogRecord;
 
+import org.assertj.core.api.InstanceOfAssertFactories;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
@@ -204,31 +205,32 @@ void ignoresSystemPropertyAndConfigFileWhenImplicitLookupsAreDisabled() {
 	@Test
 	void warnsOnMultiplePropertyResources(@TempDir Path tempDir, @TrackLogRecords LogRecordListener logRecordListener)
 			throws Exception {
+
 		Properties properties = new Properties();
 		properties.setProperty(KEY, "from second config file");
 		try (var out = Files.newOutputStream(tempDir.resolve(CONFIG_FILE_NAME))) {
 			properties.store(out, "");
 		}
+
 		ClassLoader originalClassLoader = Thread.currentThread().getContextClassLoader();
+		URL originalResource = originalClassLoader.getResource(CONFIG_FILE_NAME);
+
 		try (var customClassLoader = new URLClassLoader(new URL[] { tempDir.toUri().toURL() }, originalClassLoader)) {
 			Thread.currentThread().setContextClassLoader(customClassLoader);
 			ConfigurationParameters configParams = fromMapAndFile(Map.of(), CONFIG_FILE_NAME);
 
 			assertThat(configParams.get(KEY)).contains(CONFIG_FILE);
 
-			List<String> loggedWarnings = logRecordListener.stream(Level.WARNING) //
-					.map(LogRecord::getMessage) //
-					.toList();
-			assertThat(loggedWarnings) //
-					.hasSize(1);
-			assertThat(loggedWarnings.getFirst()) //
-					.contains("Discovered 2 '" + CONFIG_FILE_NAME
-							+ "' configuration files on the classpath (see below); only the first (*) will be used.") //
-					.contains("- "
-							+ Path.of(
-								"build/resources/test/test-junit-platform.properties").toAbsolutePath().toUri().toURL()
-							+ " (*)") //
-					.contains("- " + tempDir.resolve(CONFIG_FILE_NAME).toUri().toURL());
+			assertThat(logRecordListener.stream(Level.WARNING).map(LogRecord::getMessage)) //
+					.hasSize(1) //
+					.first(as(InstanceOfAssertFactories.STRING)) //
+					.contains("""
+							Discovered 2 '%s' configuration files on the classpath (see below); \
+							only the first (*) will be used.
+							- %s (*)
+							- %s"""//
+							.formatted(CONFIG_FILE_NAME, originalResource,
+								tempDir.resolve(CONFIG_FILE_NAME).toUri().toURL()));
 		}
 		finally {
 			Thread.currentThread().setContextClassLoader(originalClassLoader);