[Sketch] Two ways to test for errors in a more semantic way

internal/runner/file.go

@@ -2,6 +2,7 @@ package runner
 
 import (
 	"encoding/json"
+	"fmt"
 	"os"
 )
 
@@ -12,7 +13,8 @@ import (
 func readJsonFile(filename string, v any) error {
 	content, err := os.ReadFile(filename)
 	if err != nil {
-		return err
+		//return err
+		return fmt.Errorf("reading file: %w", err)
 	}
 
 	return json.Unmarshal(content, v)

internal/runner/file_test.go

@@ -0,0 +1,45 @@
+package runner
+
+import (
+	"errors"
+	"io/fs"
+	"syscall"
+	"testing"
+)
+
+type Report struct {
+	Result string `json:"result"`
+}
+
+func TestReadJsonFile_Errors(t *testing.T) {
+	var report Report
+
+	testCases := []struct {
+		fileName    string
+		wantErrorAs any
+		wantErrorIs error
+	}{
+		{
+			fileName:    "file_not_exist",
+			wantErrorAs: new(*fs.PathError),
+		},
+		{
+			fileName:    "file_not_exist",
+			wantErrorIs: syscall.ENOENT,
+		},
+	}
+
+	for _, tc := range testCases {
+		gotError := readJsonFile(tc.fileName, &report)
+		if tc.wantErrorAs != nil {
+			if !errors.As(gotError, tc.wantErrorAs) {
+				t.Errorf("readJsonFile(%q, &report) = %v, want %T", tc.fileName, gotError, tc.wantErrorAs)
+			}
+		}
+		if tc.wantErrorIs != nil {
+			if !errors.Is(gotError, tc.wantErrorIs) {
+				t.Errorf("readJsonFile(%q, &report) = %v, want %v", tc.fileName, gotError, tc.wantErrorIs)
+			}
+		}
+	}
+}