Use absolute path to input batch test file

CMakeLists.txt

@@ -105,7 +105,10 @@ install(
 # Configure the tests target.
 enable_testing()
 add_test(NAME minisolver_single COMMAND minisolver --size 1600)
-add_test(NAME minisolver_batch COMMAND minisolver --batch-input ../tests.csv)
+add_test(
+  NAME minisolver_batch 
+  COMMAND minisolver --batch-input ${PROJECT_SOURCE_DIR}/tests.csv
+)
 
 # Show final configuration report.
 include(FeatureSummary)