Set up testing

slf4j-jdk-platform-logging/pom.xml

@@ -23,6 +23,19 @@
       <groupId>org.slf4j</groupId>
       <artifactId>slf4j-api</artifactId>
     </dependency>
+
+    <dependency>
+      <groupId>org.slf4j</groupId>
+      <artifactId>slf4j-simple</artifactId>
+      <version>2.0.0-alpha0</version>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <version>${junit.version}</version>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 
   <build>

slf4j-jdk-platform-logging/src/test/java/org/slf4j/jdk/SLF4JSystemLoggerTest.java

@@ -0,0 +1,77 @@
+package org.slf4j.jdk;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.io.ByteArrayOutputStream;
+import java.io.PrintStream;
+import java.util.ArrayList;
+import java.util.ServiceLoader;
+
+import static org.junit.Assert.*;
+
+public class SLF4JSystemLoggerTest {
+
+    private static final PrintStream ERROR_OUT = System.err;
+    private static final ByteArrayOutputStream OUTPUT = new ByteArrayOutputStream();
+    private static final PrintStream ERROR_OUT_REPLACEMENT = new PrintStream(OUTPUT);
+
+    @Before
+    public void setUp() {
+        System.setErr(ERROR_OUT_REPLACEMENT);
+    }
+
+    @After
+    public void tearDown() {
+        System.setErr(ERROR_OUT);
+    }
+
+    @Test
+    public void loggerFinderLoadedAsOnlyService() {
+        // this method asserts that there is exactly one `LoggerFinder` and its of the correct type
+        getSLF4JSystemLoggerFinder();
+    }
+
+    @Test
+    public void loggerFinderReturnsLogger() {
+        var logger = getSLF4JSystemLogger();
+        assertNotNull("LoggerFinder must return logger", logger);
+    }
+
+    @Test
+    public void loggerLogsMessage() {
+        var logger = getSLF4JSystemLogger();
+        var message = "Test system logging!";
+        logger.log(System.Logger.Level.INFO, message);
+
+        String output = getOutput();
+
+        assertTrue("Captured output should contain logged message.", output.contains(message));
+    }
+
+    private static System.LoggerFinder getSLF4JSystemLoggerFinder() {
+        var loggerFinders = new ArrayList<System.LoggerFinder>();
+        // this fails when test is executed from the module path
+        // because the module declaration does not declare
+        // `uses System.LoggerFinder`
+        ServiceLoader.load(System.LoggerFinder.class).forEach(loggerFinders::add);
+        assertEquals("There should be exactly one `LoggerFinder`.", 1, loggerFinders.size());
+        var loggerFinder = loggerFinders.get(0);
+        assertEquals("The `LoggerFinder` should be of type `SLF4JSystemLoggerFinder`.",
+                     SLF4JSystemLoggerFinder.class,
+                     loggerFinder.getClass());
+        return loggerFinder;
+    }
+
+    private static System.Logger getSLF4JSystemLogger() {
+        var loggerFinder = getSLF4JSystemLoggerFinder();
+        return loggerFinder.getLogger("TestLogger", SLF4JSystemLoggerTest.class.getModule());
+    }
+
+    private static String getOutput() {
+        ERROR_OUT_REPLACEMENT.flush();
+        return OUTPUT.toString();
+    }
+
+}