Merge pull request #17 from kinbiko/fix-line-numbers

Ignore stackframes from this package in assertions

array.go

@@ -7,6 +7,9 @@ import (
 )
 
 func (a *Asserter) checkArray(path string, act, exp []interface{}) {
+	if t, ok := a.Printer.(tt); ok {
+		t.Helper()
+	}
 	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))
 		serializedAct, serializedExp := serialize(act), serialize(exp)

boolean.go

@@ -13,6 +13,9 @@ func extractBoolean(b string) (bool, error) {
 }
 
 func (a *Asserter) checkBoolean(path string, act, exp bool) {
+	if t, ok := a.Printer.(tt); ok {
+		t.Helper()
+	}
 	if act != exp {
 		a.Printer.Errorf("expected boolean at '%s' to be %v but was %v", path, exp, act)
 	}

core.go

@@ -8,6 +8,9 @@ import (
 )
 
 func (a *Asserter) pathassertf(path, act, exp string) {
+	if t, ok := a.Printer.(tt); ok {
+		t.Helper()
+	}
 	if act == exp {
 		return
 	}
@@ -102,3 +105,12 @@ func findType(j string) (jsonType, error) {
 	}
 	return jsonTypeUnknown, fmt.Errorf(`unable to identify JSON type of "%s"`, j)
 }
+
+// *testing.T has a Helper() func that allow testing tools like this package to
+// ignore their own frames when calling Errorf on *testing.T instances.
+// This interface is here to avoid breaking backwards compatibility in terms of
+// the interface we expect in New.
+type tt interface {
+	Printer
+	Helper()
+}

exports.go

@@ -54,5 +54,8 @@ func New(p Printer) *Asserter {
 // You may use "<<PRESENCE>>" against any type of value. The only exception is null, which
 // will result in an assertion failure.
 func (a *Asserter) Assertf(actualJSON, expectedJSON string, fmtArgs ...interface{}) {
+	if t, ok := a.Printer.(tt); ok {
+		t.Helper()
+	}
 	a.pathassertf("$", actualJSON, fmt.Sprintf(expectedJSON, fmtArgs...))
 }

integration_test.go

@@ -117,6 +117,84 @@ but expected JSON was:
 	}
 }
 
+type testTT struct {
+	testPrinter
+	invokedCount int
+}
+
+func (tt *testTT) Helper() {
+	tt.invokedCount++
+}
+
+func TestHelperGetsCalled(t *testing.T) {
+	testTable := []struct {
+		name     string
+		in       string
+		exp      string
+		expCount int
+	}{
+		{
+			name:     "1 at the top level, 1 for core",
+			in:       `null`,
+			exp:      `""`,
+			expCount: 2,
+		},
+		{
+			name:     "1 at the top level, 1 for core, 1 for boolean",
+			in:       `true`,
+			exp:      `false`,
+			expCount: 3,
+		},
+		{
+			name:     "1 at the top level, 1 for core, 1 for string",
+			in:       `"hello"`,
+			exp:      `"henlo"`,
+			expCount: 3,
+		},
+		{
+			name:     "1 at the top level, 1 for core, 1 for number",
+			in:       `1234`,
+			exp:      `4321`,
+			expCount: 3,
+		},
+		{
+			name:     "1 at the top level, 2 for core, 1 for object, 1 for string",
+			in:       `{"hello": "world"}`,
+			exp:      `{"hello": "世界"}`,
+			expCount: 5,
+		},
+		{
+			name:     "1 at the top level, 2 for core, 2 for object, 2 for string",
+			in:       `{"hello": {"name": "kinbiko"}}`,
+			exp:      `{"hello": {"name": "他の人"}}`,
+			expCount: 7,
+		},
+		{
+			name:     "1 at the top level, 2 for core, 1 for array, 2 for string",
+			in:       `["hello", "world"]`,
+			exp:      `["hello", "世界"]`,
+			expCount: 6,
+		},
+		{
+			name:     "1 at the top level, 4 for core, 3 for array, 4 for string",
+			in:       `[["hello", "world"], ["bye", "moon"]]`,
+			exp:      `[["hello", "世界"], ["bye", "月"]]`,
+			expCount: 13,
+		},
+	}
+
+	for _, tc := range testTable {
+		t.Run(tc.name, func(st *testing.T) {
+			tt := &testTT{}
+			ja := jsonassert.New(tt)
+			ja.Assertf(tc.in, tc.exp) // assertions should never fail
+			if got := tt.invokedCount; got != tc.expCount {
+				st.Errorf("expected %d calls to Helper but got %d", tc.expCount, got)
+			}
+		})
+	}
+}
+
 func setup() (*testPrinter, *jsonassert.Asserter) {
 	tp := &testPrinter{}
 	return tp, jsonassert.New(tp)

number.go

@@ -9,6 +9,9 @@ import (
 const minDiff = 0.000001
 
 func (a *Asserter) checkNumber(path string, act, exp float64) {
+	if t, ok := a.Printer.(tt); ok {
+		t.Helper()
+	}
 	diff := math.Abs(act - exp)
 	if diff > minDiff {
 		a.Printer.Errorf("expected number at '%s' to be '%.7f' but was '%.7f'", path, exp, act)

object.go

@@ -7,6 +7,9 @@ import (
 )
 
 func (a *Asserter) checkObject(path string, act, exp map[string]interface{}) {
+	if t, ok := a.Printer.(tt); ok {
+		t.Helper()
+	}
 	if len(act) != len(exp) {
 		a.Printer.Errorf("expected %d keys at '%s' but got %d keys", len(exp), path, len(act))
 	}

string.go

@@ -7,6 +7,9 @@ import (
 )
 
 func (a *Asserter) checkString(path, act, exp string) {
+	if t, ok := a.Printer.(tt); ok {
+		t.Helper()
+	}
 	if act != exp {
 		if len(exp+act) < 50 {
 			a.Printer.Errorf("expected string at '%s' to be '%s' but was '%s'", path, exp, act)