+.SS Structure
+Test vectors are gathered together into
+.I chunks
+which should be processed in the same way. Chunks, in turn, are grouped
+into
+.IR suites .
+.SS Functions
+The
+.B test_do
+function runs a collection of tests, as defined by
+.IR suite ,
+given the test vectors in the file
+.IR fp .
+It returns results in the
+.B test_results
+structure
+.IR results ,
+which has two members:
+.TP
+.B "unsigned tests"
+counts the number of tests carried out, and
+.TP
+.B "unsigned failed"
+counts the number of tests which failed.
+.PP
+The function returns negative if there was a system error or the test
+vector file was corrupt in some way, zero if all the tests were
+successful, or positive if some tests failed.
+.PP