Add unit test for run()

We do implicitly use run() in various tests, but are unlikely to
exercise error paths in those tests. Take care of doing so in a unit
test.

Author: tautschnig

unit/Makefile

@@ -118,6 +118,7 @@ SRC += analyses/ai/ai.cpp \
        util/prefix_filter.cpp \
        util/range.cpp \
        util/replace_symbol.cpp \
+       util/run.cpp \
        util/sharing_map.cpp \
        util/sharing_node.cpp \
        util/simplify_expr.cpp \

unit/util/run.cpp

@@ -0,0 +1,44 @@
+/*******************************************************************\
+
+Module: Unit test for run.h/run.cpp
+
+Author: Michael Tautschnig
+
+\*******************************************************************/
+
+#include <testing-utils/use_catch.h>
+
+#include <util/run.h>
+#include <util/tempfile.h>
+
+#include <fstream>
+
+SCENARIO("run() error reporting", "[core][util][run]")
+{
+  GIVEN("A command invoking a non-existent executable")
+  {
+    temporary_filet tmp_stderr("tmp.txt", "");
+
+    int result =
+      run("no-such-binary", {"no-such-binary"}, "", "", tmp_stderr());
+
+    THEN("run returns a non-zero exit code")
+    {
+      REQUIRE(result != 0);
+    }
+    THEN("run provides an error message")
+    {
+      std::ifstream read_output{tmp_stderr()};
+      std::string line;
+      REQUIRE(std::getline(read_output, line));
+#ifdef _WIN32
+      // strip terminating \r
+      REQUIRE(
+        Catch::trim(line) == "The system cannot find the file specified.");
+#else
+      REQUIRE(
+        line == "execvp no-such-binary failed: No such file or directory");
+#endif
+    }
+  }
+}