exchanges: Limit mock test JSON data size by truncating slices and maps (#1968)

* set limiter to first level mock data list and updated unit tests

* address nested slices length limit

* minor fix recording file and update unit tests

* minor updates on unit tests

* re-record mock files and minor fix on the unit tests ti adapt the mock data change

* improve http recording limit value and fix issues with mock data in binance

* added MockDataSliceLimit in request items and resolve minor unit test issues

* resolve missed conflict

* rename mock variables, resolve unit test issues, and other updates

* minor fix to CheckJSON and update unit tests

* minor unit test fix

* further optimization on mock CheckJSON method, unit tests, and re-record poloniex

* common and recording unit tests fix

* minor linter issues fix

* unit tests format fix

* fix miscellaneous error

* unit tests fix and minor docs update

* re-record and reduce mock file size

* indentation fix

* minor assertion test fix

* reverted log.Printf line in live testing

* rename variables

* update NewVCRServer unit test

* replace string comparison with *net.OpError check

* restructur net error test

* exchanges/mock: Remove redundant error assertion message in TestNewVCRServer

---------

Co-authored-by: Adrian Gallagher <adrian.gallagher@thrasher.io>

exchanges/mock/server.go

@@ -29,6 +29,11 @@ const (
 	textPlain             = "text/plain"
 )
 
+// error declarations
+var (
+	errJSONMockFilePathRequired = errors.New("no path to json mock file found")
+)
+
 // VCRMock defines the main mock JSON file and attributes
 type VCRMock struct {
 	Routes map[string]map[string][]HTTPResponse `json:"routes"`
@@ -38,7 +43,7 @@ type VCRMock struct {
 // purposes and returns the server connection details
 func NewVCRServer(path string) (string, *http.Client, error) {
 	if path == "" {
-		return "", nil, errors.New("no path to json mock file found")
+		return "", nil, errJSONMockFilePathRequired
 	}
 
 	var mockFile VCRMock
@@ -162,7 +167,7 @@ func RegisterHandler(pattern string, mock map[string][]HTTPResponse, mux *http.S
 
 				reqVals, err := DeriveURLValsFromJSONMap(readBody)
 				if err != nil {
-					log.Fatalf("Mock Test Failure - %v", err)
+					log.Fatalf("DeriveURLValsFromJSONMap Mock Test Failure - %v", err)
 				}
 
 				payload, err := MatchAndGetResponse(httpResponses, reqVals, false)