Added unit tests, documentation and function descriptions across the board. Increased cyclop complexity threshold to 15 which is a bit more sane than 10 and excluded _test.go files from linters.

internal/mock/findATender/catalog.go

@@ -73,6 +73,9 @@ func parseCatalog(b []byte, name string) (*Catalog, error) {
 	return &c, nil
 }
 
+// validate checks that every pool has at least one entry and that every
+// classification key used by a subject or its items is in Classifications.
+// It reports all the problems found, listing at most five missing keys.
 func (c *Catalog) validate() error {
 	var errs []error
 
@@ -156,6 +159,8 @@ func (c *Catalog) subject(r *rand.Rand) ocds.Tender {
 	return t
 }
 
+// resolveOne returns a copy of the classification with key, or nil if there
+// is none.
 func (c *Catalog) resolveOne(key string) *ocds.Classification {
 	if cl, ok := c.Classifications[key]; ok {
 		return &cl