Add Jenkins test case for user impersonation extension.

Author: orrc

src/main/kotlin/org/jenkinsci/plugins/slacktrigger/JenkinsExtensions.kt

@@ -3,12 +3,8 @@ package org.jenkinsci.plugins.slacktrigger
 import hudson.model.User
 import hudson.security.ACL
 import jenkins.model.Jenkins
-import org.acegisecurity.Authentication
 
 fun Jenkins.configUrl() = this.rootUrl + "configure"
 
-inline fun <R> User?.runAs(block: () -> R): R =
-        this?.let { impersonate().runAs { block() } } ?: block()
-
-inline fun <R> Authentication.runAs(block: () -> R): R =
+inline fun <R> User?.runAs(block: () -> R) =
         ACL.`as`(this).use { block() }

src/test/kotlin/org/jenkinsci/plugins/slacktrigger/JenkinsExtensionsTest.kt

@@ -0,0 +1,30 @@
+package org.jenkinsci.plugins.slacktrigger
+
+import hudson.model.User
+import org.amshove.kluent.shouldEqual
+import org.junit.Rule
+import org.junit.Test
+import org.jvnet.hudson.test.JenkinsRule
+
+class JenkinsExtensionsTest {
+
+    @get:Rule
+    val j = JenkinsRule()
+
+    @Test
+    fun `runAs without a valid user should execute as anonymous`() {
+        (null as User?).runAs {
+            User.current()?.id shouldEqual null
+        }
+    }
+
+    @Test
+    fun `runAs with a valid user should execute as that user`() {
+        j.jenkins.securityRealm = j.createDummySecurityRealm()
+
+        User.get("foo").runAs {
+            User.current()?.id shouldEqual "foo"
+        }
+    }
+
+}