refactor(netxlite/iox): group tests and avoid races (#484)

Part of https://github.com/ooni/probe/issues/1591

internal/netxlite/iox/iox_test.go

@@ -5,13 +5,14 @@ import (
 	"errors"
 	"io"
 	"strings"
+	"sync"
 	"testing"
-	"time"
 
 	"github.com/ooni/probe-cli/v3/internal/netxlite/mocks"
 )
 
-func TestReadAllContextCommonCase(t *testing.T) {
+func TestReadAllContext(t *testing.T) {
+	t.Run("with success and background context", func(t *testing.T) {
 		r := strings.NewReader("deadbeef")
 		ctx := context.Background()
 		out, err := ReadAllContext(ctx, r)
@@ -21,9 +22,9 @@ func TestReadAllContextCommonCase(t *testing.T) {
 		if len(out) != 8 {
 			t.Fatal("not the expected number of bytes")
 		}
-}
+	})
 
-func TestReadAllContextWithError(t *testing.T) {
+	t.Run("with failure and background context", func(t *testing.T) {
 		expected := errors.New("mocked error")
 		r := &mocks.Reader{
 			MockRead: func(b []byte) (int, error) {
@@ -38,10 +39,26 @@ func TestReadAllContextWithError(t *testing.T) {
 		if len(out) != 0 {
 			t.Fatal("not the expected number of bytes")
 		}
-}
+	})
 
-func TestReadAllContextWithCancelledContext(t *testing.T) {
-	r := strings.NewReader("deadbeef")
+	t.Run("with success and cancelled context", func(t *testing.T) {
+		wg := &sync.WaitGroup{}
+		wg.Add(1)
+		sigch := make(chan interface{})
+		r := &mocks.Reader{
+			MockRead: func(b []byte) (int, error) {
+				defer wg.Done()
+				<-sigch
+				// "When Read encounters an error or end-of-file condition
+				// after successfully reading n > 0 bytes, it returns
+				// the number of bytes read. It may return the (non-nil)
+				// error from the same call or return the error (and n == 0)
+				// from a subsequent call.""
+				//
+				// See https://pkg.go.dev/io#Reader
+				return len(b), io.EOF
+			},
+		}
 		ctx, cancel := context.WithCancel(context.Background())
 		cancel() // fail immediately
 		out, err := ReadAllContext(ctx, r)
@@ -51,13 +68,19 @@ func TestReadAllContextWithCancelledContext(t *testing.T) {
 		if len(out) != 0 {
 			t.Fatal("not the expected number of bytes")
 		}
-}
+		close(sigch)
+		wg.Wait()
+	})
 
-func TestReadAllContextWithErrorAndCancelledContext(t *testing.T) {
+	t.Run("with failure and cancelled context", func(t *testing.T) {
+		wg := &sync.WaitGroup{}
+		wg.Add(1)
+		sigch := make(chan interface{})
 		expected := errors.New("mocked error")
 		r := &mocks.Reader{
 			MockRead: func(b []byte) (int, error) {
-			time.Sleep(time.Millisecond)
+				defer wg.Done()
+				<-sigch
 				return 0, expected
 			},
 		}
@@ -70,9 +93,13 @@ func TestReadAllContextWithErrorAndCancelledContext(t *testing.T) {
 		if len(out) != 0 {
 			t.Fatal("not the expected number of bytes")
 		}
+		close(sigch)
+		wg.Wait()
+	})
 }
 
-func TestCopyContextCommonCase(t *testing.T) {
+func TestCopyContext(t *testing.T) {
+	t.Run("with success and background context", func(t *testing.T) {
 		r := strings.NewReader("deadbeef")
 		ctx := context.Background()
 		out, err := CopyContext(ctx, io.Discard, r)
@@ -82,9 +109,9 @@ func TestCopyContextCommonCase(t *testing.T) {
 		if out != 8 {
 			t.Fatal("not the expected number of bytes")
 		}
-}
+	})
 
-func TestCopyContextWithError(t *testing.T) {
+	t.Run("with failure and background context", func(t *testing.T) {
 		expected := errors.New("mocked error")
 		r := &mocks.Reader{
 			MockRead: func(b []byte) (int, error) {
@@ -99,10 +126,26 @@ func TestCopyContextWithError(t *testing.T) {
 		if out != 0 {
 			t.Fatal("not the expected number of bytes")
 		}
-}
+	})
 
-func TestCopyContextWithCancelledContext(t *testing.T) {
-	r := strings.NewReader("deadbeef")
+	t.Run("with success and cancelled context", func(t *testing.T) {
+		wg := &sync.WaitGroup{}
+		wg.Add(1)
+		sigch := make(chan interface{})
+		r := &mocks.Reader{
+			MockRead: func(b []byte) (int, error) {
+				defer wg.Done()
+				<-sigch
+				// "When Read encounters an error or end-of-file condition
+				// after successfully reading n > 0 bytes, it returns
+				// the number of bytes read. It may return the (non-nil)
+				// error from the same call or return the error (and n == 0)
+				// from a subsequent call.""
+				//
+				// See https://pkg.go.dev/io#Reader
+				return len(b), io.EOF
+			},
+		}
 		ctx, cancel := context.WithCancel(context.Background())
 		cancel() // fail immediately
 		out, err := CopyContext(ctx, io.Discard, r)
@@ -112,13 +155,19 @@ func TestCopyContextWithCancelledContext(t *testing.T) {
 		if out != 0 {
 			t.Fatal("not the expected number of bytes")
 		}
-}
+		close(sigch)
+		wg.Wait()
+	})
 
-func TestCopyContextWithErrorAndCancelledContext(t *testing.T) {
+	t.Run("with failure and cancelled context", func(t *testing.T) {
+		wg := &sync.WaitGroup{}
+		wg.Add(1)
+		sigch := make(chan interface{})
 		expected := errors.New("mocked error")
 		r := &mocks.Reader{
 			MockRead: func(b []byte) (int, error) {
-			time.Sleep(time.Millisecond)
+				defer wg.Done()
+				<-sigch
 				return 0, expected
 			},
 		}
@@ -131,4 +180,7 @@ func TestCopyContextWithErrorAndCancelledContext(t *testing.T) {
 		if out != 0 {
 			t.Fatal("not the expected number of bytes")
 		}
+		close(sigch)
+		wg.Wait()
+	})
 }