Jenkins - script block multiple bash commands doesn't work [duplicate] - bash

Question

I've defined If-Else in the jenkins script section. But it doesn't get executed at all. Any idea what's wrong.
script {
unit_test_result = sh (
script: ''' #!/bin/bash
mvn clean test | grep \'Tests run:\' | grep -v \'Time elapsed\'
if [[ $? == 1 ]];
then echo "No Unit tests to run!";
fi
''',
returnStdout: true
).trim()
}
But the if section doesn't run at all..
[Pipeline] script
[Pipeline]
[Pipeline]
+ grep Tests run:
+ mvn clean test
+ grep -v Time elapsed
[Pipeline] }
[Pipeline] // script
[Pipeline] }
[Pipeline] // node
[Pipeline] }
[Pipeline] // stage
[Pipeline] }
Failed in branch Unit Tests

Answer 1

grep -v 'Time elapsed' exits with status code 1 only if every input line did not contain Time elapsed, but this will never happen as mvn seems to always print a summary.
According to this website, the output of mvn clean test looks as follows if there are tests
-------------------------------------------------------
T E S T S
-------------------------------------------------------
[...]
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.547 sec
[...]
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.018 sec
Results :
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0
and according to this question, as follows if there are no tests
-------------------------------------------------------
T E S T S
-------------------------------------------------------
There are no tests to run.
Results :
Tests run: 0, Failures: 0, Errors: 0, Skipped: 0
In both cases, grep 'Tests run:' will print at least the summary in the last line. The summary never contains Time elapsed. Therefore grep -v 'Time elapsed' always exits with status code 0.
Try the following script instead:
#!/bin/bash
if ! mvn clean test | grep -q '^Tests run: [^0]'; then
echo "No Unit tests to run!";
fi
For the outputs shown in this question, we could use if mvn clean test | grep -Fxq 'There are no tests to run.' instead. But I found other sample outputs where mvn did not print that string; sometimes even no summary. The first script handles all of these cases too.