doc: notice do not create instance without New function.

Author: ghosind

assertion.go

@@ -5,6 +5,9 @@ import (
 )
 
 // Assertion is the extension of the Go builtin `testing.T`.
+//
+// Please do not create an Assertion instance without the New function, every assertion function
+// will panic if no inner testing.T set.
 type Assertion struct {
 	*testing.T
 }

assertion_test.go

@@ -16,6 +16,14 @@ func TestNewAssertion(t *testing.T) {
 	})
 }
 
+func TestAssertionWithoutNew(t *testing.T) {
+	Panic(t, func() {
+		a := new(Assertion)
+
+		a.True(true)
+	})
+}
+
 func TestRun(t *testing.T) {
 	a := New(t)
 	isSubTestRun := false