diff --git a/src/unit/engine/ArcanistConfigurationDrivenUnitTestEngine.php b/src/unit/engine/ArcanistConfigurationDrivenUnitTestEngine.php
--- a/src/unit/engine/ArcanistConfigurationDrivenUnitTestEngine.php
+++ b/src/unit/engine/ArcanistConfigurationDrivenUnitTestEngine.php
@@ -150,7 +150,7 @@
         foreach ($results as $result) {
           // If the proxied engine renders its own test results then there
           // is no need to render them again here.
-          if (!$engine->shouldEchoTestResults()) {
+          if ($engine->shouldEchoTestResults()) {
             echo $renderer->renderUnitResult($result);
           }
         }
diff --git a/src/unit/engine/PhutilUnitTestEngine.php b/src/unit/engine/PhutilUnitTestEngine.php
--- a/src/unit/engine/PhutilUnitTestEngine.php
+++ b/src/unit/engine/PhutilUnitTestEngine.php
@@ -221,4 +221,9 @@
     return $paths;
   }
 
+  public function shouldEchoTestResults() {
+    // If a renderer exists, PhutilTestCase will automatically render itself;
+    // otherwise, expect an upstream renderer to handle this.
+    return !$this->renderer;
+  }
 }