diff --git a/collector/mdadm_test.go b/collector/mdadm_test.go
index 1c83733e..06a94247 100644
--- a/collector/mdadm_test.go
+++ b/collector/mdadm_test.go
@@ -28,6 +28,6 @@ func TestMdadm(t *testing.T) {
 	}
 
 	if len(mdStates) != len(refs) {
-		t.Errorf("expected number of parsed md-device to be %s, but was %s", len(refs), len(mdStates))
+		t.Errorf("expected number of parsed md-device to be %d, but was %d", len(refs), len(mdStates))
 	}
 }
diff --git a/collector/megacli_test.go b/collector/megacli_test.go
index 3169e33f..3bd2eea7 100644
--- a/collector/megacli_test.go
+++ b/collector/megacli_test.go
@@ -29,11 +29,11 @@ func TestMegaCliAdapter(t *testing.T) {
 	}
 
 	if stats["Device Present"]["Physical Devices"] != physicalDevicesExpected {
-		t.Fatalf("Unexpected device count: %d != %d", stats["Device Present"]["Physical Devices"], physicalDevicesExpected)
+		t.Fatalf("Unexpected device count: %s != %s", stats["Device Present"]["Physical Devices"], physicalDevicesExpected)
 	}
 
 	if stats["Device Present"]["Degraded"] != virtualDevicesDegraded {
-		t.Fatal()
+		t.Fatalf("Unexpected degraded device count: %s != %s", stats["Device Present"]["Degraded"], virtualDevicesDegraded)
 	}
 }
 
@@ -56,7 +56,7 @@ func TestMegaCliDisks(t *testing.T) {
 	}
 
 	if stats[32][3]["Predictive Failure Count"] != "23" {
-		t.Fatal()
+		t.Fatalf("Unexpected predictive failure count: %s", stats[32][3]["Predictive Failure Count"])
 	}
 }