1 files changed, 144 insertions, 0 deletions
diff --git a/internal/log/rotate_test.go b/internal/log/rotate_test.go
new file mode 100644
index 0000000..5381a49
--- /dev/null
+++ b/internal/log/rotate_test.go
@@ -0,0 +1,144 @@
+package log
+
+import (
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+	"testing"
+)
+
+func createFileRotater(t *testing.T) (*FileRotater, func()) {
+	d, err := os.MkdirTemp("", "logtest")
+	if err != nil {
+		t.Fatalf("failed creating tmp dir: %v", err)
+	}
+	fn := filepath.Join(d, "test.log")
+	fr, err := NewFileRotater(fn)
+	if err != nil {
+		t.Fatalf("NewFileRotater error: %v", err)
+	}
+	if fr == nil {
+		t.Fatal("NewFileRotater returned nil")
+	}
+	return fr, func() {
+		err := os.RemoveAll(d)
+		if err != nil {
+			t.Errorf("failed removing file: %v", err)
+		}
+	}
+}
+
+func TestNewFileRotater(t *testing.T) {
+	_, cleanup := createFileRotater(t)
+	cleanup()
+
+	d, err := os.MkdirTemp("", "anotherlogtest")
+	if err != nil {
+		t.Fatalf("failed creating another tmp dir: %v", err)
+	}
+	nef := filepath.Join(d, "notexist", "test.log")
+	_, err = NewFileRotater(nef)
+	if err == nil {
+		t.Error("NewFileRotater returned no error with nonexistent dir")
+	}
+}
+
+func TestWriteConcurrent(t *testing.T) {
+	fr, cleanup := createFileRotater(t)
+	defer cleanup()
+	MaxSize = 5
+	var wg sync.WaitGroup
+	for range 5 {
+		wg.Add(1)
+		go func() {
+			_, err := fr.Write([]byte("test"))
+			defer wg.Done()
+			if err != nil {
+				t.Errorf("concurrent write returned an error: %v", err)
+			}
+		}()
+	}
+	wg.Wait()
+}
+
+func TestWriteTrim(t *testing.T) {
+	fr, cleanup := createFileRotater(t)
+	defer cleanup()
+	writeNCheckSize := func(n int, size int64) {
+		buf := make([]byte, n)
+
+		for i := 0; i < n; i++ {
+			buf[i] = 'x'
+		}
+		_, err := fr.Write(buf)
+		if err != nil {
+			t.Fatalf("failed writing: %v", err)
+		}
+
+		fs, err := fr.file.Stat()
+		if err != nil {
+			t.Fatalf("failed getting size: %v", err)
+		}
+
+		gsize := fs.Size()
+
+		if gsize != size {
+			t.Fatalf("got: %v, want: %v, max size: %v", gsize, size, MaxSize)
+		}
+	}
+
+	// we test by writing a start message and checking if it disappears after trimmign
+	// the max size we set to the length of the start message + 20 bytes
+	begS := "this is the start"
+	begB := []byte(begS)
+	startN := int64(len(begB))
+	MaxSize = startN + 20
+	TrimSize = MaxSize / 2
+
+	// no trim yet
+	_, err := fr.Write(begB)
+	if err != nil {
+		t.Fatalf("failed writing start message: %v", err)
+	}
+
+	// write until the trimming size
+	writeNCheckSize(5, startN+5)
+	writeNCheckSize(15, MaxSize)
+
+	// set the length we want to write
+	var n int64 = 11
+
+	// now the size should be the length of the trimmed message plus the remaining (non-trimmed part of the file) plus the length we want to write
+
+	size := int64(len(TrimMsg)) + (MaxSize - TrimSize) + n
+	writeNCheckSize(11, size)
+
+	// disable trimming by setting it to a high value
+	MaxSize = 9000
+	TrimSize = 9000
+
+	// now the size should be the old size plus the write size
+	newN := 12
+	writeNCheckSize(newN, size+int64(newN))
+
+	_, err = fr.file.Seek(0, io.SeekStart)
+	if err != nil {
+		t.Fatalf("failed going to beginning of file: %v", err)
+	}
+
+	b, err := io.ReadAll(fr.file)
+	if err != nil {
+		t.Fatalf("failed reading file: %v", err)
+	}
+
+	corpus := string(b)
+	if strings.Contains(corpus, begS) {
+		t.Fatalf("file still contains beginning message: %v", corpus)
+	}
+
+	if !strings.Contains(corpus, TrimMsg) {
+		t.Fatalf("file does not contain trim message: %v", corpus)
+	}
+}