[chore][pkg/stanaza] Fix and strengthen test case (open-telemetry#28228)

Follows:
open-telemetry#28206

This PR fixes a setup problem with a particular test and further
enhances it to make it more robust.

The problem was that it restarts a single operator, which is not
strictly supported behavior. Instead, a new operator should be created
from the same config.

The test involves moving a file and then validating that a log written
to the original file location is read correctly. This enhances the test
to also validate that additional logs written to the original (moved)
file will be read as well.

pkg/stanza/fileconsumer/rotation_test.go

@@ -633,31 +633,33 @@ func TestFileMovedWhileOff_BigFiles(t *testing.T) {
  operator, emitCalls := buildTestManager(t, cfg)
  persister := testutil.NewUnscopedMockPersister()
 
- log1 := tokenWithLength(1000)
- log2 := tokenWithLength(1000)
+ log1 := tokenWithLength(1001)
+ log2 := tokenWithLength(1002)
+ log3 := tokenWithLength(1003)
 
  temp := openTemp(t, tempDir)
+ tempName := temp.Name()
  writeString(t, temp, string(log1)+"\n")
- require.NoError(t, temp.Close())
 
- // Start the operator
+ // Run the operator to read the first log
  require.NoError(t, operator.Start(persister))
- defer func() {
- require.NoError(t, operator.Stop())
- }()
  waitForToken(t, emitCalls, log1)
-
- // Stop the operator, then rename and write a new log
  require.NoError(t, operator.Stop())
 
- err := os.Rename(temp.Name(), fmt.Sprintf("%s2", temp.Name()))
- require.NoError(t, err)
-
- temp = reopenTemp(t, temp.Name())
- require.NoError(t, err)
+ // Write one more log to the original file
  writeString(t, temp, string(log2)+"\n")
+ require.NoError(t, temp.Close())
+
+ // Rename the file and open another file in the same location
+ require.NoError(t, os.Rename(tempName, fmt.Sprintf("%s2", tempName)))
+
+ // Write a different log to the new file
+ temp2 := reopenTemp(t, tempName)
+ writeString(t, temp2, string(log3)+"\n")
 
  // Expect the message written to the new log to come through
- require.NoError(t, operator.Start(persister))
- waitForToken(t, emitCalls, log2)
+ operator2, emitCalls2 := buildTestManager(t, cfg)
+ require.NoError(t, operator2.Start(persister))
+ waitForTokens(t, emitCalls2, log2, log3)
+ require.NoError(t, operator2.Stop())
 }