Fix ordering bug, fix test options

build.sbt

@@ -30,13 +30,13 @@ libraryDependencies ++= Seq(
 
 Keys.fork in run := true
 
-Keys.fork in test := true
+Keys.fork in Test := true
 
-logBuffered in test := false
+logBuffered in Test := false
 
-testOptions in test += Tests.Argument("-oD")
+testOptions in Test += Tests.Argument("-oDF")
 
-javaOptions in test += "-Xss32M"
+javaOptions in Test += "-Xss32M"
 
 parallelExecution in test := false
 

src/main/scala/leon/utils/Positions.scala

@@ -19,7 +19,13 @@ abstract class Position extends Ordered[Position] {
         ld
       }
     } else {
-      0
+      if (this.file eq null) {
+        -1
+      } else if (that.file eq null) {
+        +1
+      } else {
+        this.file.getPath.compare(that.file.getPath)
+      }
     }
   }