Issue mozilla-mobile#2404: Print logcat to stdout while running unit tests.

Author: pocmo

build.gradle

@@ -72,6 +72,9 @@ subprojects {
 
             // Format test output
             tasks.matching {it instanceof Test}.all {
+                systemProperty "robolectric.logging", "stdout"
+                systemProperty "logging.test-mode", "true"
+
                 testLogging.events = []
 
                 def out = services.get(StyledTextOutputFactory).create("an-ouput")

components/support/base/src/main/java/mozilla/components/support/base/log/Log.kt

@@ -25,6 +25,8 @@ object Log {
 
     private val sinks = mutableListOf<LogSink>()
 
+    private val testMode: Boolean = System.getProperty("logging.test-mode") == "true"
+
     /**
      * Adds a sink that will receive log calls.
      */
@@ -56,6 +58,10 @@ object Log {
                 }
             }
         }
+
+        if (testMode) {
+            printTestModeMessage(priority, tag, throwable, message)
+        }
     }
 
     // Only for testing
@@ -67,6 +73,26 @@ object Log {
         }
     }
 
+    private fun printTestModeMessage(
+        priority: Priority,
+        tag: String?,
+        throwable: Throwable?,
+        message: String?
+    ) {
+        val printMessage = StringBuilder()
+        printMessage.append(priority.name[0])
+        printMessage.append(" ")
+        if (tag != null) {
+            printMessage.append("[$tag] ")
+        }
+        if (message != null) {
+            printMessage.append(message)
+        }
+
+        println(printMessage.toString())
+        throwable?.printStackTrace()
+    }
+
     /**
      * Priority constants for logging calls.
      */