fix: avoiding error and including a test

tests/crossplatform/mp_streamfile.test.sas

@@ -0,0 +1,28 @@
+/**
+  @file
+  @brief Testing mp_streamfile.sas macro
+  @details This is tricky to test as it streams to webout.  For now just
+  check the compilation, and for macro leakage.
+
+  <h4> SAS Macros </h4>
+  @li mp_assert.sas
+  @li mp_assertscope.sas
+  @li mp_streamfile.sas
+
+**/
+
+%mp_assertscope(SNAPSHOT)
+
+%mp_streamfile(iftrue(1=0)
+  ,contenttype=csv,inloc=/some/where.txt
+  ,outname=myfile.txt
+)
+
+%mp_assertscope(COMPARE)
+
+%mp_assert(
+  iftrue=(&syscc=0),
+  desc=Checking error condition,
+  outds=work.test_results
+)
+