app: consistently use t.Fatal* instead of t.Error* (except of app/vmalert and app/vmctl - these packages will be processed in a separate commit)

Consistently using t.Fatal* simplifies the test code and makes it less fragile, since it is common error
to forget to make proper cleanup after t.Error* call. Also t.Error* calls do not provide any practical
benefits when some tests fail. They just clutter test output with additional noise information,
which do not help in fixing failing tests most of the time.

This is a follow-up for a9525da8a4

app/vmagent/prometheusimport/request_handler_test.go

@@ -26,11 +26,11 @@ func TestInsertHandler(t *testing.T) {
 	req := httptest.NewRequest(http.MethodPost, "/insert/0/api/v1/import/prometheus", bytes.NewBufferString(`{"foo":"bar"}
 go_memstats_alloc_bytes_total 1`))
 	if err := InsertHandler(nil, req); err != nil {
-		t.Errorf("unxepected error %s", err)
+		t.Fatalf("unxepected error %s", err)
 	}
 	expectedMsg := "cannot unmarshal Prometheus line"
 	if !strings.Contains(testOutput.String(), expectedMsg) {
-		t.Errorf("output %q should contain %q", testOutput.String(), expectedMsg)
+		t.Fatalf("output %q should contain %q", testOutput.String(), expectedMsg)
 	}
 }
 

app/vmbackup/main_test.go

@@ -8,15 +8,18 @@ import (
 func TestHasFilepathPrefix(t *testing.T) {
 	f := func(dst, storageDataPath string, resultExpected bool) {
 		t.Helper()
+
 		result := hasFilepathPrefix(dst, storageDataPath)
 		if result != resultExpected {
-			t.Errorf("unexpected hasFilepathPrefix(%q, %q); got: %v; want: %v", dst, storageDataPath, result, resultExpected)
+			t.Fatalf("unexpected hasFilepathPrefix(%q, %q); got: %v; want: %v", dst, storageDataPath, result, resultExpected)
 		}
 	}
+
 	pwd, err := filepath.Abs("")
 	if err != nil {
 		t.Fatalf("cannot determine working directory: %s", err)
 	}
+
 	f("s3://foo/bar", "foo", false)
 	f("fs://"+pwd+"/foo", "foo", true)
 	f("fs://"+pwd+"/foo", "foo/bar", false)

app/vmselect/promql/eval_test.go

@@ -103,7 +103,7 @@ func TestGetSumInstantValues(t *testing.T) {
 
 		result := getSumInstantValues(nil, cached, start, end, timestamp)
 		if !reflect.DeepEqual(result, expectedResult) {
-			t.Errorf("unexpected result; got\n%v\nwant\n%v", result, expectedResult)
+			t.Fatalf("unexpected result; got\n%v\nwant\n%v", result, expectedResult)
 		}
 	}
 	ts := func(name string, timestamp int64, value float64) *timeseries {

app/vmselect/promql/transform_test.go

@@ -46,7 +46,7 @@ func TestVmrangeBucketsToLE(t *testing.T) {
 		result := vmrangeBucketsToLE(tss)
 		resultBuckets := timeseriesToPromMetrics(result)
 		if !reflect.DeepEqual(resultBuckets, bucketsExpected) {
-			t.Errorf("unexpected vmrangeBucketsToLE(); got\n%v\nwant\n%v", resultBuckets, bucketsExpected)
+			t.Fatalf("unexpected vmrangeBucketsToLE(); got\n%v\nwant\n%v", resultBuckets, bucketsExpected)
 		}
 	}