Fixes bug in unit tests that meant exceptions were being "hidden" from callables and uses unchecked instead of checked exceptions

.gitignore

@@ -1,2 +1,4 @@
 .flattened-pom.xml
 target
+.idea
+*.iml

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

@@ -6,6 +6,7 @@
 import java.security.Permission;
 import java.util.*;
 import java.util.concurrent.Callable;
+import java.util.stream.Collectors;
 
 import static java.lang.Class.forName;
 import static java.lang.System.*;
@@ -522,6 +523,12 @@ public static String tapSystemErr(
 		return tapStream.textThatWasWritten();
 	}
 
+	public static Collection<String> tapSystemErrToCollection(
+			Statement statement
+	) throws Exception {
+		return toCollection(tapSystemOut(statement));
+	}
+
 	/**
 	 * Executes the statement and returns the text that was written to
 	 * {@code System.err} by the statement. New line characters are replaced
@@ -581,6 +588,12 @@ public static String tapSystemOut(
 		return tapStream.textThatWasWritten();
 	}
 
+	public static Collection<String> tapSystemOutToCollection(
+			Statement statement
+	) throws Exception {
+		return toCollection(tapSystemOut(statement));
+	}
+
 	/**
 	 * Executes the statement and returns the text that was written to
 	 * {@code System.out} by the statement. New line characters are replaced
@@ -807,6 +820,13 @@ private static PrintStream wrap(
 		);
 	}
 
+	private static Collection<String> toCollection(
+			String value
+	) {
+		String[] lines = value.split(System.lineSeparator());
+		return Arrays.stream(lines).collect(Collectors.toList());
+	}
+
 	private static class DisallowWriteStream extends OutputStream {
 		@Override
 		public void write(
@@ -1111,19 +1131,20 @@ private String format(
 		 * @param <T> the type of {@code callable}'s result
 		 * @param callable an arbitrary piece of code.
 		 * @return the return value of {@code callable}.
-		 * @throws Exception any exception thrown by the callable.
 		 * @since 1.1.0
 		 * @see #withEnvironmentVariable(String, String)
 		 * @see #and(String, String)
 		 * @see #execute(Statement)
 		 */
 		public <T> T execute(
 			Callable<T> callable
-		) throws Exception {
+		) {
 			Map<String, String> originalVariables = new HashMap<>(getenv());
 			try {
 				setEnvironmentVariables();
 				return callable.call();
+			} catch (Exception e) {
+				throw new SystemLambdaExecutionException(e);
 			} finally {
 				restoreOriginalVariables(originalVariables);
 			}
@@ -1159,19 +1180,20 @@ public <T> T execute(
 		 * environment variables map. It fails if your {@code SecurityManager} forbids
 		 * such modifications.
 		 * @param statement an arbitrary piece of code.
-		 * @throws Exception any exception thrown by the statement.
 		 * @since 1.0.0
 		 * @see #withEnvironmentVariable(String, String)
 		 * @see WithEnvironmentVariables#and(String, String)
 		 * @see #execute(Callable)
 		 */
     	public void execute(
     		Statement statement
-		) throws Exception {
+		) {
     		Map<String, String> originalVariables = new HashMap<>(getenv());
     		try {
 				setEnvironmentVariables();
 				statement.execute();
+			} catch (Exception e) {
+    			throw new SystemLambdaExecutionException(e);
 			} finally {
 				restoreOriginalVariables(originalVariables);
 			}

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

@@ -0,0 +1,8 @@
+package com.github.stefanbirkner.systemlambda;
+
+public class SystemLambdaExecutionException extends RuntimeException {
+
+	public SystemLambdaExecutionException(Throwable cause) {
+		super(cause);
+	}
+}

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

@@ -0,0 +1,14 @@
+package com.github.stefanbirkner.systemlambda;
+
+import java.util.concurrent.Callable;
+
+class FailingCallableMock implements Callable<String> {
+	boolean hasBeenEvaluated = false;
+	Exception exception = new Exception("failing callable mock exception");
+
+	@Override
+	public String call() throws Exception {
+		hasBeenEvaluated = true;
+		throw exception;
+	}
+}

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

@@ -0,0 +1,12 @@
+package com.github.stefanbirkner.systemlambda;
+
+class FailingStatementMock implements Statement {
+	boolean hasBeenEvaluated = false;
+	Exception exception = new Exception("failing statement mock exception");
+
+	@Override
+	public void execute() throws Exception {
+		hasBeenEvaluated = true;
+		throw exception;
+	}
+}

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

@@ -0,0 +1,17 @@
+package com.github.stefanbirkner.systemlambda;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class SystemLambdaExecutionExceptionTest {
+
+	@Test
+	void shouldReturnCause() {
+		Throwable cause = new Exception("cause");
+
+		Throwable exception = new SystemLambdaExecutionException(cause);
+
+		assertThat(exception.getCause()).isEqualTo(cause);
+	}
+}

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

@@ -5,8 +5,12 @@
 import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
 
+import java.util.Collection;
+
 import static com.github.stefanbirkner.systemlambda.SystemLambda.tapSystemErr;
+import static com.github.stefanbirkner.systemlambda.SystemLambda.tapSystemErrToCollection;
 import static java.lang.System.err;
+import static java.lang.System.out;
 import static org.assertj.core.api.Assertions.assertThat;
 
 @DisplayNameGeneration(ReplaceUnderscores.class)
@@ -23,6 +27,17 @@ void taps_text_that_is_written_to_System_err_by_statement(
 			.isEqualTo("some text");
 	}
 
+	@Test
+	void taps_text_that_is_written_to_System_err_by_statement_to_collection(
+	) throws Exception {
+		Collection<String> linesWrittenToSystemErr = tapSystemErrToCollection(
+				() -> { out.println("some text"); out.println("more text"); }
+		);
+
+		assertThat(linesWrittenToSystemErr)
+				.containsExactly("some text", "more text");
+	}
+
 	@Test
 	void tapped_text_is_empty_when_statement_does_not_write_to_System_err(
 	) throws Exception {
@@ -31,7 +46,7 @@ void tapped_text_is_empty_when_statement_does_not_write_to_System_err(
 		);
 
 		assertThat(textWrittenToSystemErr)
-			.isEqualTo("");
+			.isEmpty();
 	}
 
 	@Nested

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

@@ -5,7 +5,10 @@
 import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
 
+import java.util.Collection;
+
 import static com.github.stefanbirkner.systemlambda.SystemLambda.tapSystemOut;
+import static com.github.stefanbirkner.systemlambda.SystemLambda.tapSystemOutToCollection;
 import static java.lang.System.*;
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -23,6 +26,17 @@ void taps_text_that_is_written_to_System_out_by_statement(
 			.isEqualTo("some text");
 	}
 
+	@Test
+	void taps_text_that_is_written_to_System_out_by_statement_to_collection(
+	) throws Exception {
+		Collection<String> linesWrittenToSystemOut = tapSystemOutToCollection(
+				() -> { out.println("some text"); out.println("more text"); }
+		);
+
+		assertThat(linesWrittenToSystemOut)
+				.containsExactly("some text", "more text");
+	}
+
 	@Test
 	void tapped_text_is_empty_when_statement_does_not_write_to_System_out(
 	) throws Exception {
@@ -31,7 +45,7 @@ void tapped_text_is_empty_when_statement_does_not_write_to_System_out(
 		);
 
 		assertThat(textWrittenToSystemOut)
-			.isEqualTo("");
+			.isEmpty();
 	}
 
 	@Nested