fix when fixture.Install logs 'ignoring AGENT_KEEP_INSTALLED...' (#3380)

(cherry picked from commit 3372e6f)

pkg/testing/fixture_install.go

@@ -12,11 +12,8 @@ import (
 	"os"
 	"path/filepath"
 	"strconv"
-	"strings"
 	"time"
 
-	"github.com/stretchr/testify/require"
-
 	"github.com/elastic/elastic-agent/internal/pkg/agent/application/paths"
 	"github.com/elastic/elastic-agent/pkg/control/v2/client"
 	"github.com/elastic/elastic-agent/pkg/core/process"
@@ -128,22 +125,14 @@ func (f *Fixture) Install(ctx context.Context, installOpts *InstallOpts, opts ..
 
 		// environment variable AGENT_KEEP_INSTALLED=true will skip the uninstall
 		// useful to debug the issue with the Elastic Agent
+		if f.t.Failed() && keepInstalled() {
+			f.t.Logf("skipping uninstall; test failed and AGENT_KEEP_INSTALLED=true")
+			return
+		}
+
 		if keepInstalled() {
-			f.t.Logf("skipping uninstall; AGENT_KEEP_INSTALLED=true")
-		} else {
-			out, err := f.Uninstall(ctx, &UninstallOpts{Force: true, UninstallToken: f.uninstallToken})
-			f.setClient(nil)
-			if err != nil &&
-				(errors.Is(err, ErrNotInstalled) ||
-					strings.Contains(
-						err.Error(),
-						"elastic-agent: no such file or directory")) {
-				// Agent fixture has already been uninstalled, perhaps by
-				// an explicit call to fixture.Uninstall, so nothing needs
-				// to be done here.
-				return
-			}
-			require.NoErrorf(f.t, err, "uninstalling agent failed. Output: %q", out)
+			f.t.Logf("ignoring AGENT_KEEP_INSTALLED=true as test succeeded, " +
+				"keeping the agent installed will jeopardise other tests")
 		}
 	})