Adding simple ability for multiple responses from a test server

ghttp/handlers.go

@@ -10,6 +10,7 @@ import (
 	"net/url"
 	"reflect"
 	"strings"
+	"sync/atomic"
 
 	"github.com/golang/protobuf/proto"
 	"github.com/onsi/gomega"
@@ -401,3 +402,53 @@ func RespondWithJSONEncodedPtr(statusCode *int, object interface{}, optionalHead
 func RespondWithProto(statusCode int, message proto.Message, optionalHeader ...http.Header) http.HandlerFunc {
 	return NewGHTTPWithGomega(gomega.Default).RespondWithProto(statusCode, message, optionalHeader...)
 }
+
+var noOpHandler = func(_ http.ResponseWriter, _ *http.Request) {
+	// empty function for Nop
+}
+
+//RespondWithMultiple
+//This function combines a set of handlers into a handler such that each handler gets called in succession until
+//the last handler. In this case when the last handler is reached it will keep responding with this handler.
+//In the case of the RoundRobinWithMultiple combination handler the once the last handler is reached it will
+//start at the beginning again. This is useful for testing retry behaviour of clients.
+//I.E. A sequence of 500 500 500 200.... should be good enough for a retry to succeed.
+func RespondWithMultiple(handlers ...http.HandlerFunc) http.HandlerFunc {
+	var responseNumber int32 = 0
+	if len(handlers) > 0 {
+		return func(w http.ResponseWriter, req *http.Request) {
+			responseNum := atomic.LoadInt32(&responseNumber)
+			handlerNumber := min(responseNum, int32(len(handlers)-1))
+			handlers[handlerNumber](w, req)
+			atomic.AddInt32(&responseNumber, 1)
+		}
+	}
+	return noOpHandler
+}
+
+//RoundRobinWithMultiple
+//This function combines a set of handlers into a single handler such that each handler gets called in succession until
+//the last handler. Once the last handler is reached it will start at the beginning.
+//In the case of the RespondWithMultiple combination handler the once the last handler is reached it will
+//keep responding with the last handler.
+// This is useful for stress testing retry behaviour over time.
+//I.E. A sequence of 200 200 500 500 200 repeating can be called by many routines at the same time to
+//imitate more complex behavior
+func RoundRobinWithMultiple(handlers ...http.HandlerFunc) http.HandlerFunc {
+	var responseNumber int32 = 0
+	if len(handlers) > 0 {
+		return func(w http.ResponseWriter, req *http.Request) {
+			handlerNumber := atomic.LoadInt32(&responseNumber) % int32(len(handlers))
+			handlers[handlerNumber](w, req)
+			atomic.AddInt32(&responseNumber, 1)
+		}
+	}
+	return noOpHandler
+}
+
+func min(one, two int32) int32 {
+	if one < two {
+		return one
+	}
+	return two
+}

ghttp/handlers_test.go

@@ -0,0 +1,114 @@
+package ghttp_test
+
+import (
+	"fmt"
+	. "github.com/onsi/ginkgo/v2"
+	. "github.com/onsi/gomega"
+	. "github.com/onsi/gomega/ghttp"
+	"io"
+	"net/http"
+)
+
+var _ = Describe("Handlers test", func() {
+	Describe("RespondWithMultiple", func() {
+		value := -1
+		handlers := RespondWithMultiple(
+			func(resp http.ResponseWriter, req *http.Request) { value = 1 },
+			func(resp http.ResponseWriter, req *http.Request) { value = 2 },
+			func(resp http.ResponseWriter, req *http.Request) { value = 3 },
+			func(resp http.ResponseWriter, req *http.Request) { value = 4 },
+			func(resp http.ResponseWriter, req *http.Request) { value = 5 },
+		)
+		DescribeTable("Should rotate through each handler and repeat last handler",
+			func(expected int) {
+				handlers(nil, nil)
+				Expect(value).To(Equal(expected))
+			},
+			Entry("call 1", 1),
+			Entry("call 2", 2),
+			Entry("call 3", 3),
+			Entry("call 4", 4),
+			Entry("call 5", 5),
+			Entry("call 6", 5),
+		)
+	})
+
+	Describe("RoundRobinWithMultiple", func() {
+		value := -1
+		handlers := RoundRobinWithMultiple(
+			func(resp http.ResponseWriter, req *http.Request) { value = 1 },
+			func(resp http.ResponseWriter, req *http.Request) { value = 2 },
+			func(resp http.ResponseWriter, req *http.Request) { value = 3 },
+			func(resp http.ResponseWriter, req *http.Request) { value = 4 },
+			func(resp http.ResponseWriter, req *http.Request) { value = 5 },
+		)
+		DescribeTable("Should rotate through each and start at the beginning again",
+			func(expected int) {
+				handlers(nil, nil)
+				Expect(value).To(Equal(expected))
+			},
+			Entry("call 1", 1),
+			Entry("call 2", 2),
+			Entry("call 3", 3),
+			Entry("call 4", 4),
+			Entry("call 5", 5),
+			Entry("call 6", 1),
+		)
+	})
+})
+
+func ExampleRespondWithMultiple() {
+	server := NewServer()
+	server.RouteToHandler(http.MethodGet, "/example",
+		RespondWithMultiple(
+			RespondWith(http.StatusOK, "1"),
+			RespondWith(http.StatusOK, "2"),
+			RespondWith(http.StatusNotFound, "Not found"),
+			RespondWith(http.StatusOK, "3"),
+			RespondWith(http.StatusInternalServerError, "Internal server error"),
+		))
+	for i := 0; i < 6; i++ {
+		resp, err := http.Get(server.URL() + "/example")
+		if err != nil {
+			panic(err)
+		}
+		defer resp.Body.Close()
+		body, _ := io.ReadAll(resp.Body)
+		fmt.Printf("%d - %s\n", resp.StatusCode, string(body))
+	}
+
+	// Output: 200 - 1
+	// 200 - 2
+	// 404 - Not found
+	// 200 - 3
+	// 500 - Internal server error
+	// 500 - Internal server error
+}
+
+func ExampleRoundRobinWithMultiple() {
+	server := NewServer()
+	server.RouteToHandler(http.MethodGet, "/example",
+		RoundRobinWithMultiple(
+			RespondWith(http.StatusOK, "1"),
+			RespondWith(http.StatusOK, "2"),
+			RespondWith(http.StatusNotFound, "Not found"),
+			RespondWith(http.StatusOK, "3"),
+			RespondWith(http.StatusInternalServerError, "Internal server error"),
+		))
+	for i := 0; i < 6; i++ {
+		resp, err := http.Get(server.URL() + "/example")
+		if err != nil {
+			panic(err)
+		}
+		defer resp.Body.Close()
+		body, _ := io.ReadAll(resp.Body)
+		fmt.Printf("%d - %s\n", resp.StatusCode, string(body))
+	}
+
+	// Output: 200 - 1
+	// 200 - 2
+	// 404 - Not found
+	// 200 - 3
+	// 500 - Internal server error
+	// 200 - 1
+}