Add methods for tapping err and out simultaneously

The output of command-line applications is usually the output to the
standard output stream and the error output stream intermixed. The new
methods allow capturing the intermixed output.

    @test
    void application_writes_text_to_System_err_and_out(
    ) throws Exception {
      String text = tapSystemErrAndOut(() -> {
        System.err.print("text from err");
        System.out.print("text from out");
      });
      assertEquals("text from errtext from out", text);
    }

    @test
    void application_writes_mutliple_lines_to_System_err_and_out(
    ) throws Exception {
      String text = tapSystemErrAndOutNormalized(() -> {
        System.err.println("text from err");
        System.out.println("text from out");
      });
      assertEquals("text from err\ntext from out\n", text);
    }

README.md

@@ -20,7 +20,7 @@ System Lambda is available from
 <dependency>
     <groupId>com.github.stefanbirkner</groupId>
     <artifactId>system-lambda</artifactId>
-    <version>1.1.1</version>
+    <version>1.2.0</version>
 </dependency>
 ```
 
@@ -113,8 +113,9 @@ void execute_code_that_manipulates_system_properties(
 
 Command-line applications usually write to the console. If you write such
 applications you need to test the output of these applications. The methods
-`tapSystemErr`, `tapSystemErrNormalized`, `tapSystemOut` and
-`tapSystemOutNormalized` allow you to tap the text that is written to
+`tapSystemErr`, `tapSystemErrNormalized`, `tapSystemOut`,
+`tapSystemOutNormalized`, `tapSystemErrAndOut` and
+`tapSystemErrAndOutNormalized` allow you to tap the text that is written to
 `System.err`/`System.out`. The methods with the suffix `Normalized` normalize
 line breaks to `\n` so that you can run tests with the same assertions on
 different operating systems.
@@ -157,6 +158,26 @@ void application_writes_mutliple_lines_to_System_out(
   });
   assertEquals("first line\nsecond line\n", text);
 }
+
+@Test
+void application_writes_text_to_System_err_and_out(
+) throws Exception {
+  String text = tapSystemErrAndOut(() -> {
+    System.err.print("text from err");
+    System.out.print("text from out");
+  });
+  assertEquals("text from errtext from out", text);
+}
+
+@Test
+void application_writes_mutliple_lines_to_System_err_and_out(
+) throws Exception {
+  String text = tapSystemErrAndOutNormalized(() -> {
+    System.err.println("text from err");
+    System.out.println("text from out");
+  });
+  assertEquals("text from err\ntext from out\n", text);
+}
 ```
 
 You can assert that nothing is written to `System.err`/`System.out` by wrapping

pom.xml

@@ -9,7 +9,7 @@
   </parent>
 
   <artifactId>system-lambda</artifactId>
-  <version>1.2.0-SNAPSHOT</version>
+  <version>1.2.0</version>
   <packaging>jar</packaging>
 
   <name>System Lambda</name>

src/main/java/com/github/stefanbirkner/systemlambda/SystemLambda.java

@@ -87,8 +87,11 @@
  * applications you need to test the output of these applications. The methods
  * {@link #tapSystemErr(Statement) tapSystemErr},
  * {@link #tapSystemErrNormalized(Statement) tapSystemErrNormalized},
- * {@link #tapSystemOut(Statement) tapSystemOut} and
- * {@link #tapSystemOutNormalized(Statement) tapSystemOutNormalized} allow you
+ * {@link #tapSystemOut(Statement) tapSystemOut},
+ * {@link #tapSystemOutNormalized(Statement) tapSystemOutNormalized},
+ * {@link #tapSystemErrAndOut(Statement) tapSystemErrAndOut} and
+ * {@link #tapSystemErrAndOutNormalized(Statement) tapSystemErrAndOutNormalized}
+ * allow you
  * to tap the text that is written to {@code System.err}/{@code System.out}. The
  * methods with the suffix {@code Normalized} normalize line breaks to
  * {@code \n} so that you can run tests with the same assertions on different
@@ -131,6 +134,26 @@
  *     System.out.println("second line");
  *   });
  *   assertEquals(text, "first line\nsecond line\n");
+ * }
+ *
+ * @Test
+ * void application_writes_text_to_System_err_and_out(
+ * ) throws Exception {
+ *   String text = tapSystemErrAndOut((){@literal ->} {
+ *     System.err.print("text from err");
+ *     System.out.print("text from out");
+ *   });
+ *   assertEquals("text from errtext from out", text);
+ * }
+ *
+ * @Test
+ * void application_writes_mutliple_lines_to_System_err_and_out(
+ * ) throws Exception {
+ *   String text = tapSystemErrAndOutNormalized((){@literal ->} {
+ *     System.err.println("text from err");
+ *     System.out.println("text from out");
+ *   });
+ *   assertEquals("text from err\ntext from out\n", text);
  * }</pre>
  *
  * <p>You can assert that nothing is written to
@@ -509,6 +532,8 @@ public static void restoreSystemProperties(
 	 * @return text that is written to {@code System.err} by the statement.
 	 * @throws Exception any exception thrown by the statement.
 	 * @see #tapSystemOut(Statement)
+	 * @see #tapSystemErrAndOut(Statement)
+	 * @see #tapSystemErrAndOutNormalized(Statement)
 	 * @since 1.0.0
 	 */
 	public static String tapSystemErr(
@@ -541,6 +566,8 @@ public static String tapSystemErr(
 	 * @return text that is written to {@code System.err} by the statement.
 	 * @throws Exception any exception thrown by the statement.
 	 * @see #tapSystemOut(Statement)
+	 * @see #tapSystemErrAndOut(Statement)
+	 * @see #tapSystemErrAndOutNormalized(Statement)
 	 * @since 1.0.0
 	 */
 	public static String tapSystemErrNormalized(
@@ -550,6 +577,80 @@ public static String tapSystemErrNormalized(
 			.replace(lineSeparator(), "\n");
 	}
 
+	/**
+	 * Executes the statement and returns the text that was written to
+	 * {@code System.err} and {@code System.out} by the statement.
+	 * <pre>
+	 * &#064;Test
+	 * void application_writes_text_to_System_err_and_out(
+	 * ) throws Exception {
+	 *   String text = tapSystemErrAndOut((){@literal ->} {
+	 *     System.err.print("text from err");
+	 *     System.out.print("text from out");
+	 *   });
+	 *   assertEquals("text from errtext from out", text);
+	 * }
+	 * </pre>
+	 *
+	 * @param statement an arbitrary piece of code.
+	 * @return text that is written to {@code System.err} and {@code System.out}
+	 * by the statement.
+	 * @throws Exception any exception thrown by the statement.
+	 * @see #tapSystemErrAndOutNormalized(Statement)
+	 * @see #tapSystemErr(Statement)
+	 * @see #tapSystemErrNormalized(Statement)
+	 * @see #tapSystemOut(Statement)
+	 * @see #tapSystemOutNormalized(Statement)
+	 * @since 1.2.0
+	 */
+	public static String tapSystemErrAndOut(
+		Statement statement
+	) throws Exception {
+		TapStream tapStream = new TapStream();
+		executeWithSystemErrReplacement(
+			tapStream,
+			() -> executeWithSystemOutReplacement(
+					tapStream,
+					statement
+			)
+		);
+		return tapStream.textThatWasWritten();
+	}
+
+	/**
+	 * Executes the statement and returns the text that was written to
+	 * {@code System.err} and {@code System.out} by the statement. New line
+	 * characters are replaced with a single {@code \n}.
+	 * <pre>
+	 * &#064;Test
+	 * void application_writes_mutliple_lines_to_System_err_and_out(
+	 * ) throws Exception {
+	 *   String text = tapSystemErrAndOutNormalized((){@literal ->} {
+	 *     System.err.println("text from err");
+	 *     System.out.println("text from out");
+	 *   });
+	 *   assertEquals("text from err\ntext from out\n", text);
+	 * }
+	 * </pre>
+	 *
+	 * @param statement an arbitrary piece of code.
+	 * @return text that is written to {@code System.err} and {@code System.out}
+	 * by the statement.
+	 * @throws Exception any exception thrown by the statement.
+	 * @see #tapSystemErrAndOut(Statement)
+	 * @see #tapSystemErr(Statement)
+	 * @see #tapSystemErrNormalized(Statement)
+	 * @see #tapSystemOut(Statement)
+	 * @see #tapSystemOutNormalized(Statement)
+	 * @since 1.2.0
+	 */
+	public static String tapSystemErrAndOutNormalized(
+		Statement statement
+	) throws Exception {
+		return tapSystemErrAndOut(statement)
+			.replace(lineSeparator(), "\n");
+	}
+
 	/**
 	 * Executes the statement and returns the text that was written to
 	 * {@code System.out} by the statement.
@@ -568,6 +669,8 @@ public static String tapSystemErrNormalized(
 	 * @return text that is written to {@code System.out} by the statement.
 	 * @throws Exception any exception thrown by the statement.
 	 * @see #tapSystemErr(Statement)
+	 * @see #tapSystemErrAndOut(Statement)
+	 * @see #tapSystemErrAndOutNormalized(Statement)
 	 * @since 1.0.0
 	 */
 	public static String tapSystemOut(
@@ -600,6 +703,8 @@ public static String tapSystemOut(
 	 * @return text that is written to {@code System.out} by the statement.
 	 * @throws Exception any exception thrown by the statement.
 	 * @see #tapSystemErr(Statement)
+	 * @see #tapSystemErrAndOut(Statement)
+	 * @see #tapSystemErrAndOutNormalized(Statement)
 	 * @since 1.0.0
 	 */
 	public static String tapSystemOutNormalized(

src/test/java/com/github/stefanbirkner/systemlambda/TapSystemErrAndOutNormalizedTest.java

@@ -0,0 +1,60 @@
+package com.github.stefanbirkner.systemlambda;
+
+import org.junit.jupiter.api.DisplayNameGeneration;
+import org.junit.jupiter.api.DisplayNameGenerator.ReplaceUnderscores;
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Test;
+
+import static com.github.stefanbirkner.systemlambda.SystemLambda.*;
+import static java.lang.System.err;
+import static java.lang.System.out;
+import static org.assertj.core.api.Assertions.assertThat;
+
+@DisplayNameGeneration(ReplaceUnderscores.class)
+class TapSystemErrAndOutNormalizedTest {
+
+	@Test
+	void taps_text_that_is_written_to_System_err_and_out_by_statement_has_only_slash_n_for_new_line(
+	) throws Exception {
+		String textWrittenToSystemErr = tapSystemErrAndOutNormalized(
+				() -> {
+					err.println("line 1");
+					out.println("line 2");
+					err.println("line 3");
+					out.println("line 4");
+				}
+		);
+
+		assertThat(textWrittenToSystemErr)
+				.isEqualTo("line 1\nline 2\nline 3\nline 4\n");
+	}
+
+	@Test
+	void tapped_text_is_empty_when_statement_does_not_write_to_System_err_nor_out(
+	) throws Exception {
+		String textWrittenToSystemErr = tapSystemErrAndOutNormalized(
+				() -> {}
+		);
+
+		assertThat(textWrittenToSystemErr)
+				.isEqualTo("");
+	}
+
+	@Nested
+	class System_err_is_same_as_before
+			extends RestoreSystemErrChecks
+	{
+		System_err_is_same_as_before() {
+			super(SystemLambda::tapSystemErrAndOutNormalized);
+		}
+	}
+
+	@Nested
+	class System_out_is_same_as_before
+			extends RestoreSystemOutChecks
+	{
+		System_out_is_same_as_before() {
+			super(SystemLambda::tapSystemErrAndOutNormalized);
+		}
+	}
+}

src/test/java/com/github/stefanbirkner/systemlambda/TapSystemErrAndOutTest.java

@@ -0,0 +1,61 @@
+package com.github.stefanbirkner.systemlambda;
+
+import org.junit.jupiter.api.DisplayNameGeneration;
+import org.junit.jupiter.api.DisplayNameGenerator.ReplaceUnderscores;
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Test;
+
+import static com.github.stefanbirkner.systemlambda.SystemLambda.tapSystemErr;
+import static com.github.stefanbirkner.systemlambda.SystemLambda.tapSystemErrAndOut;
+import static java.lang.System.err;
+import static java.lang.System.out;
+import static org.assertj.core.api.Assertions.assertThat;
+
+@DisplayNameGeneration(ReplaceUnderscores.class)
+class TapSystemErrAndOutTest {
+
+	@Test
+	void taps_text_that_is_written_to_System_err_and_out_by_statement(
+	) throws Exception {
+		String textWrittenToSystemErrAndOut = tapSystemErrAndOut(
+			() -> {
+				err.print("word1 ");
+				out.print("word2 ");
+				err.print("word3 ");
+				out.print("word4 ");
+			}
+		);
+
+		assertThat(textWrittenToSystemErrAndOut)
+			.isEqualTo("word1 word2 word3 word4 ");
+	}
+
+	@Test
+	void tapped_text_is_empty_when_statement_does_not_write_to_System_err_nor_out(
+	) throws Exception {
+		String textWrittenToSystemErrAndOut = tapSystemErrAndOut(
+			() -> {}
+		);
+
+		assertThat(textWrittenToSystemErrAndOut)
+			.isEqualTo("");
+	}
+
+	@Nested
+	class System_err_is_same_as_before
+			extends RestoreSystemErrChecks
+	{
+		System_err_is_same_as_before() {
+			super(SystemLambda::tapSystemErrAndOut);
+		}
+	}
+
+	@Nested
+	class System_out_is_same_as_before
+			extends RestoreSystemOutChecks
+	{
+		System_out_is_same_as_before() {
+			super(SystemLambda::tapSystemErrAndOut);
+		}
+	}
+}