terraform test: Include test case execution time in JUnit XML

Our currently-experimental JUnit XML output didn't previously include the
"time" attribute for test runs at all, but from testing with common JUnit
XML consumers we've learned that populating this is effectively mandatory
because otherwise software just assumes that it's zero, producing a
misleading result.

We'll now populate it based on the test runner's measure of the execution
time, assuming that the test runner actually measured it. If not, we'll
leave it omitted and thus get the same behavior as before, which in
practice means that most software will treat it as zero anyway.

Because JUnit XML output is still experimental with the goal of getting
feedback on exactly how we map the Terraform testing model onto that
Java-oriented format, this is intentionally not supported for remote test
runs in Terraform Cloud yet. It isn't really practical for Terraform Cloud
to participate in short-lived Terraform CLI experiments, because Terraform
Cloud has a different release schedule than Terraform CLI does. However,
if this experiment is successful then we will eventually need to find a
way to plumb this additional information through the JSON logs and ensure
that it arrives in the locally-generated JUnit XML output.

Author: apparentlymart

internal/command/views/test.go

@@ -886,6 +886,19 @@ func junitXMLTestReport(suite *moduletest.Suite) ([]byte, error) {
 				Failure   *WithMessage `xml:"failure,omitempty"`
 				Error     *WithMessage `xml:"error,omitempty"`
 				Stderr    *WithMessage `xml:"system-err,omitempty"`
+
+				// RunTime is the time spent executing the run associated
+				// with this test case, in seconds with the fractional component
+				// representing partial seconds.
+				//
+				// We assume here that it's not practically possible for an
+				// execution to take literally zero fractional seconds at
+				// the accuracy we're using here (nanoseconds converted into
+				// floating point seconds) and so use zero to represent
+				// "not known", and thus omit that case. (In practice many
+				// JUnit XML consumers treat the absense of this attribute
+				// as zero anyway.)
+				RunTime float64 `xml:"time,attr,omitempty"`
 			}
 
 			testCase := TestCase{
@@ -898,6 +911,9 @@ func junitXMLTestReport(suite *moduletest.Suite) ([]byte, error) {
 				// Java-shaped languages.
 				Classname: file.Name,
 			}
+			if execMeta := run.ExecutionMeta; execMeta != nil {
+				testCase.RunTime = execMeta.Duration.Seconds()
+			}
 			switch run.Status {
 			case moduletest.Skip:
 				testCase.Skipped = &WithMessage{