Merge pull request #16170 from prometheus/fix-test-logging-race

Fix test race by not calling t.Log() after test completion

cmd/prometheus/main_test.go

@@ -26,6 +26,7 @@ import (
 	"runtime"
 	"strconv"
 	"strings"
+	"sync"
 	"syscall"
 	"testing"
 	"time"
@@ -246,7 +247,12 @@ func TestWALSegmentSizeBounds(t *testing.T) {
 			// Log stderr in case of failure.
 			stderr, err := prom.StderrPipe()
 			require.NoError(t, err)
+
+			// WaitGroup is used to ensure that we don't call t.Log() after the test has finished.
+			var wg sync.WaitGroup
+			wg.Add(1)
 			go func() {
+				defer wg.Done()
 				slurp, _ := io.ReadAll(stderr)
 				t.Log(string(slurp))
 			}()
@@ -264,6 +270,7 @@ func TestWALSegmentSizeBounds(t *testing.T) {
 					prom.Process.Kill()
 					<-done
 				}
+				wg.Wait()
 				return
 			}
 
@@ -273,6 +280,8 @@ func TestWALSegmentSizeBounds(t *testing.T) {
 			require.ErrorAs(t, err, &exitError)
 			status := exitError.Sys().(syscall.WaitStatus)
 			require.Equal(t, tc.exitCode, status.ExitStatus())
+
+			wg.Wait()
 		})
 	}
 }
@@ -497,7 +506,12 @@ func TestModeSpecificFlags(t *testing.T) {
 			// Log stderr in case of failure.
 			stderr, err := prom.StderrPipe()
 			require.NoError(t, err)
+
+			// WaitGroup is used to ensure that we don't call t.Log() after the test has finished.
+			var wg sync.WaitGroup
+			wg.Add(1)
 			go func() {
+				defer wg.Done()
 				slurp, _ := io.ReadAll(stderr)
 				t.Log(string(slurp))
 			}()
@@ -515,6 +529,7 @@ func TestModeSpecificFlags(t *testing.T) {
 					prom.Process.Kill()
 					<-done
 				}
+				wg.Wait()
 				return
 			}
 
@@ -527,6 +542,8 @@ func TestModeSpecificFlags(t *testing.T) {
 			} else {
 				t.Errorf("unable to retrieve the exit status for prometheus: %v", err)
 			}
+
+			wg.Wait()
 		})
 	}
 }