Add unit tests for new logging in GaugeManager using GaugeCounter.

firebase-perf/src/main/java/com/google/firebase/perf/session/gauges/GaugeCounter.kt

@@ -14,6 +14,8 @@
 
 package com.google.firebase.perf.session.gauges
 
+import androidx.annotation.VisibleForTesting
+import com.google.firebase.perf.logging.AndroidLogger
 import java.util.concurrent.atomic.AtomicInteger
 
 /**
@@ -23,17 +25,31 @@ import java.util.concurrent.atomic.AtomicInteger
 object GaugeCounter {
   private const val MAX_METRIC_COUNT = 25
   private val counter = AtomicInteger(0)
-  private val gaugeManager: GaugeManager = GaugeManager.getInstance()
+  private val logger = AndroidLogger.getInstance()
+
+  @set:VisibleForTesting(otherwise = VisibleForTesting.NONE)
+  @set:JvmStatic
+  var gaugeManager: GaugeManager = GaugeManager.getInstance()
 
   fun incrementCounter() {
     val metricsCount = counter.incrementAndGet()
 
     if (metricsCount >= MAX_METRIC_COUNT) {
       gaugeManager.logGaugeMetrics()
     }
+
+    logger.debug("Incremented logger to $metricsCount")
   }
 
   fun decrementCounter() {
-    counter.decrementAndGet()
+    val curr = counter.decrementAndGet()
+    logger.debug("Decremented logger to $curr")
   }
+
+  @VisibleForTesting(otherwise = VisibleForTesting.NONE)
+  fun resetCounter() {
+    counter.set(0)
+  }
+
+  @VisibleForTesting(otherwise = VisibleForTesting.NONE) fun count(): Int = counter.get()
 }

firebase-perf/src/main/java/com/google/firebase/perf/session/gauges/GaugeManager.java

@@ -100,13 +100,19 @@ public void initializeGaugeMetadataManager(Context appContext) {
 
   @Override
   public void onUpdateAppState(ApplicationProcessState applicationProcessState) {
-    this.applicationProcessState = applicationProcessState;
-
+    // If it isn't a verbose session (or unset) update the app state and return.
     if (session == null || !session.isVerbose()) {
+      this.applicationProcessState = applicationProcessState;
       return;
     }
 
-    // If it's a verbose session, start collecting gauges for the new app state.
+    // Log existing gauges to the current app state.
+    logGaugeMetrics();
+
+    // Update App State.
+    this.applicationProcessState = applicationProcessState;
+
+    // Start collecting gauges for the new app state.
     startCollectingGauges(this.applicationProcessState, session.getTimer());
   }
 
@@ -132,6 +138,7 @@ public void startCollectingGauges(PerfSession session) {
       stopCollectingGauges();
     }
 
+    // TODO(b/394127311): Explore always setting the app state as FOREGROUND.
     ApplicationProcessState gaugeCollectionApplicationProcessState = applicationProcessState;
     if (gaugeCollectionApplicationProcessState
         == ApplicationProcessState.APPLICATION_PROCESS_STATE_UNKNOWN) {
@@ -419,4 +426,9 @@ private long getMemoryGaugeCollectionFrequencyMs(
       return memoryGaugeCollectionFrequency;
     }
   }
+
+  @VisibleForTesting
+  void setApplicationProcessState(ApplicationProcessState applicationProcessState) {
+    this.applicationProcessState = applicationProcessState;
+  }
 }

firebase-perf/src/test/java/com/google/firebase/perf/FirebasePerformanceTestBase.java

@@ -25,9 +25,11 @@
 import com.google.firebase.perf.config.ConfigResolver;
 import com.google.firebase.perf.session.PerfSession;
 import com.google.firebase.perf.session.SessionManager;
+import com.google.firebase.perf.session.gauges.GaugeCounter;
 import com.google.firebase.perf.util.ImmutableBundle;
 import org.junit.After;
 import org.junit.Before;
+import org.junit.BeforeClass;
 import org.robolectric.shadows.ShadowPackageManager;
 
 public class FirebasePerformanceTestBase {
@@ -54,6 +56,12 @@ public class FirebasePerformanceTestBase {
 
   protected Context appContext;
 
+  @BeforeClass
+  public static void setUpBeforeClass() {
+    // TODO(b/394127311): Explore removing this.
+    GaugeCounter.INSTANCE.resetCounter();
+  }
+
   @Before
   public void setUpFirebaseApp() {
     appContext = ApplicationProvider.getApplicationContext();