be friendlier with the assert message when the JSON representation ar…

…e very long

array.go

@@ -9,7 +9,12 @@ import (
 func (a *Asserter) checkArray(path string, act, exp []interface{}) {
 	if len(act) != len(exp) {
 		a.Printer.Errorf("length of arrays at '%s' were different. Expected array to be of length %d, but contained %d element(s)", path, len(exp), len(act))
-		a.Printer.Errorf("actual JSON at '%s' was: %+v, but expected JSON was: %+v", path, serialize(act), serialize(exp))
+		serializedAct, serializedExp := serialize(act), serialize(exp)
+		if len(serializedAct+serializedExp) < 50 {
+			a.Printer.Errorf("actual JSON at '%s' was: %+v, but expected JSON was: %+v", path, serializedAct, serializedExp)
+		} else {
+			a.Printer.Errorf("actual JSON at '%s' was:\n%+v\nbut expected JSON was:\n%+v", path, serializedAct, serializedExp)
+		}
 		return
 	}
 	for i := range act {

integration_test.go

@@ -32,6 +32,12 @@ func TestAssertf(t *testing.T) {
 		{name: "identical strings", act: `"hello world"`, exp: `"hello world"`, msgs: []string{}},
 		{name: "identical empty strings", act: `""`, exp: `""`, msgs: []string{}},
 		{name: "different strings", act: `"hello"`, exp: `"world"`, msgs: []string{`expected string at '$' to be 'world' but was 'hello'`}},
+		{name: "different strings", act: `"lorem ipsum dolor sit amet lorem ipsum dolor sit amet"`, exp: `"lorem ipsum dolor sit amet lorem ipsum dolor sit amet why do I have to be the test string?"`, msgs: []string{
+			`expected string at '$' to be
+'lorem ipsum dolor sit amet lorem ipsum dolor sit amet why do I have to be the test string?'
+but was
+'lorem ipsum dolor sit amet lorem ipsum dolor sit amet'`,
+		}},
 		{name: "empty v non-empty string", act: `""`, exp: `"world"`, msgs: []string{`expected string at '$' to be 'world' but was ''`}},
 		{name: "identical objects", act: `{"hello": "world"}`, exp: `{"hello":"world"}`, msgs: []string{}},
 		{name: "different keys in objects", act: `{"world": "hello"}`, exp: `{"hello":"world"}`, msgs: []string{
@@ -57,6 +63,13 @@ func TestAssertf(t *testing.T) {
 			`length of arrays at '$' were different. Expected array to be of length 0, but contained 1 element(s)`,
 			`actual JSON at '$' was: [null], but expected JSON was: []`,
 		}},
+		{name: "non-empty array v empty array", act: `[1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6,7,8,9,0]`, exp: `[1,0,1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6,7,8,9,0]`, msgs: []string{
+			`length of arrays at '$' were different. Expected array to be of length 22, but contained 30 element(s)`,
+			`actual JSON at '$' was:
+[1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6,7,8,9,0]
+but expected JSON was:
+[1,0,1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6,7,8,9,0]`,
+		}},
 		{name: "identical non-empty arrays", act: `["hello"]`, exp: `["hello"]`, msgs: []string{}},
 		{name: "different non-empty arrays", act: `["hello"]`, exp: `["world"]`, msgs: []string{
 			`expected string at '$[0]' to be 'world' but was 'hello'`,

string.go

@@ -8,7 +8,11 @@ import (
 
 func (a *Asserter) checkString(path, act, exp string) {
 	if act != exp {
-		a.Printer.Errorf("expected string at '%s' to be '%s' but was '%s'", path, exp, act)
+		if len(exp+act) < 50 {
+			a.Printer.Errorf("expected string at '%s' to be '%s' but was '%s'", path, exp, act)
+		} else {
+			a.Printer.Errorf("expected string at '%s' to be\n'%s'\nbut was\n'%s'", path, exp, act)
+		}
 	}
 }