SCMSourceRetrieverTest: rename checkDefaultVersion() to checkDefaultVersionStaticStrings() and limit influence of caller-defined BRANCH_NAME [JENKINS-69731]

Author: jimklimov

src/test/java/org/jenkinsci/plugins/workflow/libs/SCMSourceRetrieverTest.java

@@ -219,7 +219,7 @@ public class SCMSourceRetrieverTest {
     }
 
     @Issue("JENKINS-69731")
-    @Test public void checkDefaultVersion() throws Exception {
+    @Test public void checkDefaultVersionStaticStrings() throws Exception {
         sampleRepo.init();
         sampleRepo.write("vars/myecho.groovy", "def call() {echo 'something special'}");
         sampleRepo.git("add", "vars");
@@ -253,11 +253,14 @@ public class SCMSourceRetrieverTest {
         WorkflowRun b2 = r.buildAndAssertSuccess(p2);
         r.assertLogContains("something very special", b2);
 
-        // Branch context for job not set - fall back to default
-        WorkflowJob p3 = r.jenkins.createProject(WorkflowJob.class, "p3");
-        p3.setDefinition(new CpsFlowDefinition("@Library('branchylib@${BRANCH_NAME}') import myecho; myecho()", true));
-        WorkflowRun b3 = r.buildAndAssertSuccess(p3);
-        r.assertLogContains("something special", b3);
+        // Do not let caller-provided BRANCH_NAME interfere here
+        if (System.getenv("BRANCH_NAME") == null) {
+            // Branch context for job not set - fall back to default
+            WorkflowJob p3 = r.jenkins.createProject(WorkflowJob.class, "p3");
+            p3.setDefinition(new CpsFlowDefinition("@Library('branchylib@${BRANCH_NAME}') import myecho; myecho()", true));
+            WorkflowRun b3 = r.buildAndAssertSuccess(p3);
+            r.assertLogContains("something special", b3);
+        }
 
         // Use a specified but missing branch
         WorkflowJob p4 = r.jenkins.createProject(WorkflowJob.class, "p4");