show container logs when expected port isn't available

matchers/serve.go

@@ -1,6 +1,7 @@
 package matchers
 
 import (
+	"errors"
 	"fmt"
 	"io"
 	"net/http"
@@ -81,7 +82,11 @@ func (sm *ServeMatcher) Match(actual interface{}) (success bool, err error) {
 
 	if _, ok := container.Ports[port]; !ok {
 		// EITHER: you have multiple ports and didn't specify OR you specified a bad port
-		return false, fmt.Errorf("ServeMatcher looking for response from container port %s which is not in container port map", port)
+		message := fmt.Sprintf("ServeMatcher looking for response from container port %s which is not in container port map", port)
+		if logs, _ := sm.docker.Container.Logs.Execute(container.ID); logs != nil {
+			message = fmt.Sprintf("%s\n\nContainer logs:\n\n%s", message, logs)
+		}
+		return false, errors.New(message)
 	}
 
 	response, err := sm.client.Get(fmt.Sprintf("http://%s:%s%s", container.Host(), container.HostPort(port), sm.endpoint))

matchers/serve_test.go

@@ -207,7 +207,15 @@ func testServe(t *testing.T, context spec.G, it spec.S) {
 		context("failure cases", func() {
 			context("the port is not in the container port mapping", func() {
 				it.Before(func() {
-					matcher = matcher.OnPort(8080)
+					executable := &fakes.Executable{}
+					executable.ExecuteCall.Stub = func(execution pexec.Execution) error {
+						fmt.Fprintln(execution.Stdout, "some logs")
+						return nil
+					}
+
+					docker := occam.NewDocker().WithExecutable(executable)
+
+					matcher = matchers.Serve("some string").WithDocker(docker).OnPort(8080)
 				})
 
 				it("returns an error", func() {
@@ -216,6 +224,7 @@ func testServe(t *testing.T, context spec.G, it spec.S) {
 						Env:   map[string]string{"PORT": "8080"},
 					})
 					Expect(err).To(MatchError(ContainSubstring("ServeMatcher looking for response from container port 8080 which is not in container port map")))
+					Expect(err).To(MatchError(ContainSubstring("Container logs:\n\nsome logs\n")))
 					Expect(result).To(BeFalse())
 				})
 			})