Initial commit

src/test/java/ch/unibas/dmi/dbis/cs108/example/HelloWorldTest.java

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+package ch.unibas.dmi.dbis.cs108.example;
+
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.io.ByteArrayOutputStream;
+import java.io.PrintStream;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/**
+ * An example test class.
+ * Checks the output of the {@link HelloWorld} class and makes sure it contains "Hello World"
+ */
+public class HelloWorldTest {
+
+    /*
+     * Streams to store system.out and system.err content
+     */
+    private ByteArrayOutputStream outStream = new ByteArrayOutputStream();
+    private ByteArrayOutputStream errStream = new ByteArrayOutputStream();
+
+    /*
+     * Here we store the previous pointers to system.out / system.err
+     */
+    private PrintStream outBackup;
+    private PrintStream errBackup;
+
+    /**
+     * This method is executed before each test.
+     * It redirects System.out and System.err to our variables {@link #outStream} and {@link #errStream}.
+     * This allows us to test their content later.
+     */
+    @BeforeEach
+    public void redirectStdOutStdErr() {
+        outBackup = System.out;
+        errBackup = System.err;
+        System.setOut(new PrintStream(outStream));
+        System.setErr(new PrintStream(errStream));
+    }
+
+    /**
+     * This method is run after each test.
+     * It redirects System.out / System.err back to the normal streams.
+     */
+    @AfterEach
+    public void reestablishStdOutStdErr() {
+        System.setOut(outBackup);
+        System.setErr(errBackup);
+    }
+
+    /**
+     * This is a normal JUnit-Test. It executes the HelloWorld-Method and verifies that it actually wrote "Hello World" to stdout
+     */
+    @Test
+    public void testMain() {
+        HelloWorld.main(new String[0]);
+        String toTest = outStream.toString();
+        toTest = removeNewline(toTest);
+        assertTrue(toTest.contains("Hello World"));
+    }
+
+    private static String removeNewline(String str) {
+        return str.replace("\n", "").replace("\r", "");
+    }
+}