diff --git a/core/jni/android_util_Process.cpp b/core/jni/android_util_Process.cpp
index 2d7069c50255e..f929dde4dcd17 100644
--- a/core/jni/android_util_Process.cpp
+++ b/core/jni/android_util_Process.cpp
@@ -644,6 +644,12 @@ static jlong android_os_Process_getTotalMemory(JNIEnv* env, jobject clazz)
     return si.totalram;
 }
 
+/*
+ * The outFields array is initialized to -1 to allow the caller to identify
+ * when the status file (and therefore the process) they specified is invalid.
+ * This array should not be overwritten or cleared before we know that the
+ * status file can be read.
+ */
 void android_os_Process_readProcLines(JNIEnv* env, jobject clazz, jstring fileStr,
                                       jobjectArray reqFields, jlongArray outFields)
 {
@@ -692,14 +698,14 @@ void android_os_Process_readProcLines(JNIEnv* env, jobject clazz, jstring fileSt
         return;
     }
 
-    //ALOGI("Clearing %" PRId32 " sizes", count);
-    for (i=0; i<count; i++) {
-        sizesArray[i] = 0;
-    }
-
     int fd = open(file.string(), O_RDONLY | O_CLOEXEC);
 
     if (fd >= 0) {
+        //ALOGI("Clearing %" PRId32 " sizes", count);
+        for (i=0; i<count; i++) {
+            sizesArray[i] = 0;
+        }
+
         const size_t BUFFER_SIZE = 4096;
         char* buffer = (char*)malloc(BUFFER_SIZE);
         int len = read(fd, buffer, BUFFER_SIZE-1);
diff --git a/core/tests/coretests/src/android/os/ProcessTest.java b/core/tests/coretests/src/android/os/ProcessTest.java
index b749e715316a9..6b02764b7f28c 100644
--- a/core/tests/coretests/src/android/os/ProcessTest.java
+++ b/core/tests/coretests/src/android/os/ProcessTest.java
@@ -17,13 +17,12 @@
 
 package android.os;
 
-import androidx.test.filters.MediumTest;
-
 import junit.framework.TestCase;
 
 public class ProcessTest extends TestCase {
 
-    @MediumTest
+    private static final int BAD_PID = 0;
+
     public void testProcessGetUidFromName() throws Exception {
         assertEquals(android.os.Process.SYSTEM_UID, Process.getUidForName("system"));
         assertEquals(Process.BLUETOOTH_UID, Process.getUidForName("bluetooth"));
@@ -35,7 +34,6 @@ public class ProcessTest extends TestCase {
                 Process.getUidForName("u3_a100"));
     }
 
-    @MediumTest
     public void testProcessGetUidFromNameFailure() throws Exception {
         // Failure cases
         assertEquals(-1, Process.getUidForName("u2a_foo"));
@@ -47,4 +45,29 @@ public class ProcessTest extends TestCase {
         assertEquals(-1, Process.getUidForName("u2jhsajhfkjhsafkhskafhkashfkjashfkjhaskjfdhakj3"));
     }
 
+    /**
+     * Tests getUidForPid() by ensuring that it returns the correct value when the process queried
+     * doesn't exist.
+     */
+    public void testGetUidForPidInvalidPid() {
+        assertEquals(-1, Process.getUidForPid(BAD_PID));
+    }
+
+    /**
+     * Tests getParentPid() by ensuring that it returns the correct value when the process queried
+     * doesn't exist.
+     */
+    public void testGetParentPidInvalidPid() {
+        assertEquals(-1, Process.getParentPid(BAD_PID));
+    }
+
+    /**
+     * Tests getThreadGroupLeader() by ensuring that it returns the correct value when the
+     * thread queried doesn't exist.
+     */
+    public void testGetThreadGroupLeaderInvalidTid() {
+        // This function takes a TID instead of a PID but BAD_PID should also be a bad TID.
+        assertEquals(-1, Process.getThreadGroupLeader(BAD_PID));
+    }
+
 }