diff --git a/org.eclipse.jgit.pgm.test/src/org/eclipse/jgit/lib/CLIRepositoryTestCase.java b/org.eclipse.jgit.pgm.test/src/org/eclipse/jgit/lib/CLIRepositoryTestCase.java
index 4bf9b43..a72af9a 100644
--- a/org.eclipse.jgit.pgm.test/src/org/eclipse/jgit/lib/CLIRepositoryTestCase.java
+++ b/org.eclipse.jgit.pgm.test/src/org/eclipse/jgit/lib/CLIRepositoryTestCase.java
@@ -48,11 +48,13 @@
 import java.io.IOException;
 import java.nio.file.Path;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 
 import org.eclipse.jgit.junit.JGitTestUtil;
 import org.eclipse.jgit.junit.LocalDiskRepositoryTestCase;
 import org.eclipse.jgit.pgm.CLIGitCommand;
+import org.eclipse.jgit.pgm.Die;
 import org.junit.Before;
 
 public class CLIRepositoryTestCase extends LocalDiskRepositoryTestCase {
@@ -79,7 +81,7 @@ public void setUp() throws Exception {
 	 * @return command output
 	 * @throws Exception
 	 */
-	protected String[] execute(String... cmds) throws Exception {
+	protected String[] executeUnchecked(String... cmds) throws Exception {
 		List<String> result = new ArrayList<String>(cmds.length);
 		for (String cmd : cmds) {
 			result.addAll(CLIGitCommand.execute(cmd, db));
@@ -88,6 +90,28 @@ public void setUp() throws Exception {
 	}
 
 	/**
+	 * Executes specified git commands (with arguments), throws exception and
+	 * stops execution on first command which output contains a 'fatal:' error
+	 *
+	 * @param cmds
+	 *            each string argument must be a valid git command line, e.g.
+	 *            "git branch -h"
+	 * @return command output
+	 * @throws Exception
+	 */
+	protected String[] execute(String... cmds) throws Exception {
+		List<String> result = new ArrayList<String>(cmds.length);
+		for (String cmd : cmds) {
+			List<String> out = CLIGitCommand.execute(cmd, db);
+			if (contains(out, "fatal: ")) {
+				throw new Die(toString(out));
+			}
+			result.addAll(out);
+		}
+		return result.toArray(new String[0]);
+	}
+
+	/**
 	 * @param link
 	 *            the path of the symbolic link to create
 	 * @param target
@@ -196,15 +220,32 @@ protected void assertStringArrayEquals(String expected, String[] actual) {
 	}
 
 	protected void assertArrayOfLinesEquals(String[] expected, String[] actual) {
-		assertEquals(toText(expected), toText(actual));
+		assertEquals(toString(expected), toString(actual));
 	}
 
-	private static String toText(String[] lines) {
+	public static String toString(String[] lines) {
+		return toString(Arrays.asList(lines));
+	}
+
+	public static String toString(List<String> lines) {
 		StringBuilder b = new StringBuilder();
 		for (String s : lines) {
-			b.append(s);
-			b.append('\n');
+			if (s != null && !s.isEmpty()) {
+				b.append(s);
+				if (!s.endsWith("\n")) {
+					b.append('\n');
+				}
+			}
 		}
 		return b.toString();
 	}
+
+	public static boolean contains(List<String> lines, String str) {
+		for (String s : lines) {
+			if (s.contains(str)) {
+				return true;
+			}
+		}
+		return false;
+	}
 }
diff --git a/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/AddTest.java b/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/AddTest.java
index ca3f00f..5970913 100644
--- a/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/AddTest.java
+++ b/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/AddTest.java
@@ -65,7 +65,7 @@ public void setUp() throws Exception {
 	@Test
 	public void testAddNothing() throws Exception {
 		assertEquals("fatal: Argument \"filepattern\" is required", //
-				execute("git add")[0]);
+				executeUnchecked("git add")[0]);
 	}
 
 	@Test
diff --git a/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/ArchiveTest.java b/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/ArchiveTest.java
index 9aca2d8..2e02c76 100644
--- a/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/ArchiveTest.java
+++ b/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/ArchiveTest.java
@@ -102,7 +102,8 @@ public void testEmptyTar() throws Exception {
 	@Test
 	public void testUnrecognizedFormat() throws Exception {
 		String[] expect = new String[] { "fatal: Unknown archive format 'nonsense'" };
-		String[] actual = execute("git archive --format=nonsense " + emptyTree);
+		String[] actual = executeUnchecked(
+				"git archive --format=nonsense " + emptyTree);
 		assertArrayEquals(expect, actual);
 	}
 
diff --git a/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/BranchTest.java b/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/BranchTest.java
index 4200cd0..f369577 100644
--- a/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/BranchTest.java
+++ b/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/BranchTest.java
@@ -89,6 +89,6 @@ public void testListContains() throws Exception {
 	@Test
 	public void testExistingBranch() throws Exception {
 		assertEquals("fatal: A branch named 'master' already exists.",
-				execute("git branch master")[0]);
+				executeUnchecked("git branch master")[0]);
 	}
 }
diff --git a/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/CheckoutTest.java b/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/CheckoutTest.java
index 167d8ab..6175b6c 100644
--- a/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/CheckoutTest.java
+++ b/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/CheckoutTest.java
@@ -109,13 +109,13 @@ public void testCheckoutNewBranchThatAlreadyExists() throws Exception {
 
 		assertStringArrayEquals(
 				"fatal: A branch named 'master' already exists.",
-				execute("git checkout -b master"));
+				executeUnchecked("git checkout -b master"));
 	}
 
 	@Test
 	public void testCheckoutNewBranchOnBranchToBeBorn() throws Exception {
 		assertStringArrayEquals("fatal: You are on a branch yet to be born",
-				execute("git checkout -b side"));
+				executeUnchecked("git checkout -b side"));
 	}
 
 	@Test
diff --git a/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/CommitTest.java b/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/CommitTest.java
index 360ee5a..721ed15 100644
--- a/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/CommitTest.java
+++ b/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/CommitTest.java
@@ -98,16 +98,4 @@ public void testCommitAll() throws Exception {
 				result.trim().equals("On branch master"));
 	}
 
-	String toString(String[] arr) {
-		StringBuilder sb = new StringBuilder();
-		for (String s : arr) {
-			if (s != null && !s.isEmpty()) {
-				sb.append(s);
-				if (!s.endsWith("\n")) {
-					sb.append('\n');
-				}
-			}
-		}
-		return sb.toString();
-	}
 }
diff --git a/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/DescribeTest.java b/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/DescribeTest.java
index 1c8ba0c..a50b243 100644
--- a/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/DescribeTest.java
+++ b/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/DescribeTest.java
@@ -73,7 +73,7 @@ private void initialCommitAndTag() throws Exception {
 	public void testNoHead() throws Exception {
 		assertArrayEquals(
 				new String[] { "fatal: No names found, cannot describe anything." },
-				execute("git describe"));
+				executeUnchecked("git describe"));
 	}
 
 	@Test
@@ -81,7 +81,7 @@ public void testHeadNoTag() throws Exception {
 		git.commit().setMessage("initial commit").call();
 		assertArrayEquals(
 				new String[] { "fatal: No names found, cannot describe anything." },
-				execute("git describe"));
+				executeUnchecked("git describe"));
 	}
 
 	@Test
@@ -119,7 +119,7 @@ public void testHelpArgumentBeforeUnknown() throws Exception {
 
 	@Test
 	public void testHelpArgumentAfterUnknown() throws Exception {
-		String[] output = execute("git describe -XYZ -h");
+		String[] output = executeUnchecked("git describe -XYZ -h");
 		String all = Arrays.toString(output);
 		assertTrue("Unexpected help output: " + all,
 				all.contains("jgit describe"));
diff --git a/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/MergeTest.java b/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/MergeTest.java
index 975e8c4..641e59b 100644
--- a/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/MergeTest.java
+++ b/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/MergeTest.java
@@ -195,7 +195,7 @@ public void testNoFastForward() throws Exception {
 	@Test
 	public void testNoFastForwardAndSquash() throws Exception {
 		assertEquals("fatal: You cannot combine --squash with --no-ff.",
-				execute("git merge master --no-ff --squash")[0]);
+				executeUnchecked("git merge master --no-ff --squash")[0]);
 	}
 
 	@Test
@@ -210,7 +210,7 @@ public void testFastForwardOnly() throws Exception {
 		git.commit().setMessage("commit#2").call();
 
 		assertEquals("fatal: Not possible to fast-forward, aborting.",
-				execute("git merge master --ff-only")[0]);
+				executeUnchecked("git merge master --ff-only")[0]);
 	}
 
 	@Test
diff --git a/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/RepoTest.java b/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/RepoTest.java
index 85fc1db..7156827 100644
--- a/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/RepoTest.java
+++ b/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/RepoTest.java
@@ -103,7 +103,7 @@ public void setUp() throws Exception {
 	@Test
 	public void testMissingPath() throws Exception {
 		assertEquals("fatal: Argument \"path\" is required",
-				execute("git repo")[0]);
+				executeUnchecked("git repo")[0]);
 	}
 
 	/**
diff --git a/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/TagTest.java b/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/TagTest.java
index ab09db5..0fe25f5 100644
--- a/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/TagTest.java
+++ b/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/TagTest.java
@@ -68,6 +68,6 @@ public void testTagTwice() throws Exception {
 		git.commit().setMessage("commit").call();
 
 		assertEquals("fatal: tag 'test' already exists",
-				execute("git tag test")[0]);
+				executeUnchecked("git tag test")[0]);
 	}
 }