Fixes test file collisions with high concurrency builds
Fix by Ninpo <ninpo@qap.la>
https://bugs.gentoo.org/909759, https://github.com/OpenShot/libopenshot/issues/933

--- a/tests/FFmpegWriter.cpp
+++ b/tests/FFmpegWriter.cpp
@@ -34,7 +34,7 @@ TEST_CASE( "Webm", "[libopenshot][ffmpegwriter]" )
 	r.Open();
 
 	/* WRITER ---------------- */
-	FFmpegWriter w("output1.webm");
+	FFmpegWriter w("Webm-output1.webm");
 
 	// Set options
 	w.SetAudioOptions(true, "libvorbis", 44100, 2, LAYOUT_STEREO, 188000);
@@ -50,7 +50,7 @@ TEST_CASE( "Webm", "[libopenshot][ffmpegwriter]" )
 	w.Close();
 	r.Close();
 
-	FFmpegReader r1("output1.webm");
+	FFmpegReader r1("Webm-output1.webm");
 	r1.Open();
 
 	// Verify various settings on new MP4
@@ -81,7 +81,7 @@ TEST_CASE( "Options_Overloads", "[libopenshot][ffmpegwriter]" )
 	r.Open();
 
 	/* WRITER ---------------- */
-	FFmpegWriter w("output1.mp4");
+	FFmpegWriter w("Options_Overloads-output1.mp4");
 
 	// Set options
 	w.SetAudioOptions("aac", 48000, 192000);
@@ -97,7 +97,7 @@ TEST_CASE( "Options_Overloads", "[libopenshot][ffmpegwriter]" )
 	w.Close();
 	r.Close();
 
-	FFmpegReader r1("output1.mp4");
+	FFmpegReader r1("Options_Overloads-output1.mp4");
 	r1.Open();
 
 	// Verify implied settings
@@ -123,7 +123,7 @@ TEST_CASE( "DisplayInfo", "[libopenshot][ffmpegwriter]" )
 	r.Open();
 
 	/* WRITER ---------------- */
-	FFmpegWriter w("output1.webm");
+	FFmpegWriter w("DisplayInfo-output1.webm");
 
 	// Set options
 	w.SetAudioOptions(true, "libvorbis", 44100, 2, LAYOUT_STEREO, 188000);
@@ -203,7 +203,7 @@ TEST_CASE( "Gif", "[libopenshot][ffmpegwriter]" )
     t.Open();
 
     /* WRITER ---------------- */
-    FFmpegWriter w("output1.gif");
+    FFmpegWriter w("Gif-output1.gif");
 
     // Set options (no audio options are set)
     w.SetVideoOptions(true, "gif", Fraction(24,1), 1280, 720, Fraction(1,1), false, false, 15000000);
@@ -221,7 +221,7 @@ TEST_CASE( "Gif", "[libopenshot][ffmpegwriter]" )
     w.Close();
     t.Close();
 
-    FFmpegReader r1("output1.gif");
+    FFmpegReader r1("Gif-output1.gif");
     r1.Open();
 
     // Verify various settings on new Gif
--- a/tests/ImageWriter.cpp
+++ b/tests/ImageWriter.cpp
@@ -64,7 +64,7 @@ TEST_CASE( "Gif", "[libopenshot][imagewriter]" )
 	r.Open();
 
 	/* WRITER ---------------- */
-	ImageWriter w("output1.gif");
+	ImageWriter w("ImageWriter-Gif-output1.gif");
 
 	CHECK_FALSE(w.IsOpen());
 
@@ -87,7 +87,7 @@ TEST_CASE( "Gif", "[libopenshot][imagewriter]" )
 	r.Close();
 
 	// Open up the 5th frame from the newly created GIF
-	ImageReader r1("output1.gif[4]");
+	ImageReader r1("ImageWriter-Gif-output1.gif[4]");
 
 	// Basic Reader state queries
 	CHECK(r1.Name() == "ImageReader");