Switch to ginkgo/gomega for tests

This switches over to ginkgo/gomega for tests, which makes writing
certain tests easier/more fluent in the future.

vendor/github.com/onsi/gomega/internal/oraclematcher/oracle_matcher.go

@@ -0,0 +1,25 @@
+package oraclematcher
+
+import "github.com/onsi/gomega/types"
+
+/*
+GomegaMatchers that also match the OracleMatcher interface can convey information about
+whether or not their result will change upon future attempts.
+
+This allows `Eventually` and `Consistently` to short circuit if success becomes impossible.
+
+For example, a process' exit code can never change.  So, gexec's Exit matcher returns `true`
+for `MatchMayChangeInTheFuture` until the process exits, at which point it returns `false` forevermore.
+*/
+type OracleMatcher interface {
+	MatchMayChangeInTheFuture(actual interface{}) bool
+}
+
+func MatchMayChangeInTheFuture(matcher types.GomegaMatcher, value interface{}) bool {
+	oracleMatcher, ok := matcher.(OracleMatcher)
+	if !ok {
+		return true
+	}
+
+	return oracleMatcher.MatchMayChangeInTheFuture(value)
+}