diff --git a/Makefile b/Makefile
index 5fd00f8..ada2462 100644
--- a/Makefile
+++ b/Makefile
@@ -87,10 +87,7 @@ define TEST_template =
 	@if [ -e $$(@D).log ]; then \
 	    cmp $$(TESTTMPDIR)/$(testname).log $$(@D).log || ( \
 	        echo "Failed test $$(@D)"; \
-	        echo "Was expecting on STDOUT:"; \
-	        cat $$(@D).log; \
-	        echo "Observed on STDOUT:"; \
-	        cat $$(TESTTMPDIR)/$(testname).log; \
+		diff -u $$(@D).log $$(TESTTMPDIR)/$(testname).log; \
 	        exit 1; \
 	    ); \
 	elif [ -s $$(TESTTMPDIR)/$(testname).log ]; then \
@@ -104,10 +101,7 @@ define TEST_template =
 	@if [ -e $$(@D).out ]; then \
 	    cmp $$(TESTTMPDIR)/$(testname).out $$(@D).out || ( \
 	        echo "Failed test $$(@D)"; \
-	        echo "Was expecting on STDOUT:"; \
-	        cat $$(@D).out; \
-	        echo "Observed on STDOUT:"; \
-	        cat $$(TESTTMPDIR)/$(testname).out; \
+		diff -u $$(@D).out $$(TESTTMPDIR)/$(testname).out; \
 	        exit 1; \
 	    ); \
 	elif [ -s $$(TESTTMPDIR)/$(testname).out ]; then \
@@ -121,10 +115,7 @@ define TEST_template =
 	@if [ -e $$(@D).err ]; then \
 	    cmp $$(TESTTMPDIR)/$(testname).err $$(@D).err || ( \
 	        echo "Failed test $$(@D)"; \
-	        echo "Was expecting on STDERR:"; \
-	        cat $$(@D).err; \
-	        echo "Observed on STDERR:"; \
-	        cat $$(TESTTMPDIR)/$(testname).err; \
+		diff -u $$(@D).err $$(TESTTMPDIR)/$(testname).err; \
 	        exit 1; \
 	    ); \
 	elif [ -s $$(TESTTMPDIR)/$(testname).err ]; then \
diff --git a/t3.c b/t3.c
index 2dfb735..92358f6 100644
--- a/t3.c
+++ b/t3.c
@@ -89,9 +89,6 @@ struct message *stderr_head = NULL;
 struct message *stderr_tail = NULL;
 int stderr_queuelen = 0;
 
-// Mutex for thread-safe access to the queues
-// TODO: remove because we are not using threads
-
 static void usage(const int rc) {
   printf("Usage: t3 [OPTION] FILE -- COMMAND ARGS ...\n");
   printf("Invoke provided command and write its colorized, "
diff --git a/tests/fibonacci.args b/tests/fibonacci.args
index 07e56ab..b235255 100644
--- a/tests/fibonacci.args
+++ b/tests/fibonacci.args
@@ -1 +1 @@
--- sh -c 'n=100; x=0; y=1; z=$x; function out() { if [ `expr $1 % 2` -eq 0 ]; then echo "$1: evens to stdout"; else echo "$1: odds to stderr" 1>&2; fi }; for i in `seq 1 $n`; do x=`expr $x + $y`; y=$z; z=$x; out $x; done'
+-- bash -c 'n=100; x=0; y=1; z=$x; function out() { if [ `expr $1 % 2` -eq 0 ]; then echo "$1: evens to stdout"; else echo "$1: odds to stderr" 1>&2; fi }; for i in `seq 1 $n`; do x=`expr $x + $y`; y=$z; z=$x; out $x; done'