feat: backend service

backend/push/cursor_test.go

@@ -0,0 +1,79 @@
+package push
+
+import (
+	"sync"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestCursorGeneratorMonotonicAndConcurrent(t *testing.T) {
+	t.Parallel()
+
+	var g cursorGenerator
+	const goroutines = 64
+	const perGoroutine = 1000
+	results := make(chan uint64, goroutines*perGoroutine)
+	var wg sync.WaitGroup
+	wg.Add(goroutines)
+	for range goroutines {
+		go func() {
+			defer wg.Done()
+			for range perGoroutine {
+				results <- g.next()
+			}
+		}()
+	}
+	wg.Wait()
+	close(results)
+
+	seen := make(map[uint64]struct{}, goroutines*perGoroutine)
+	var max uint64
+	for n := range results {
+		_, dup := seen[n]
+		require.Falsef(t, dup, "duplicate cursor %d", n)
+		seen[n] = struct{}{}
+		if n > max {
+			max = n
+		}
+	}
+	assert.EqualValues(t, goroutines*perGoroutine, max)
+}
+
+func TestFormatAndParseCursor(t *testing.T) {
+	t.Parallel()
+
+	cases := []struct {
+		in  uint64
+		out string
+	}{
+		{0, "00000000000000000000"},
+		{1, "00000000000000000001"},
+		{1234567890, "00000000001234567890"},
+	}
+	for _, tc := range cases {
+		s := formatCursor(tc.in)
+		assert.Equal(t, tc.out, s)
+		assert.Len(t, s, cursorWidth)
+		n, ok := parseCursor(s)
+		require.True(t, ok)
+		assert.Equal(t, tc.in, n)
+	}
+
+	n, ok := parseCursor("")
+	assert.True(t, ok)
+	assert.Zero(t, n)
+
+	n, ok = parseCursor("not-a-number")
+	assert.False(t, ok)
+	assert.Zero(t, n)
+}
+
+func TestFormatCursorLexicographicOrder(t *testing.T) {
+	t.Parallel()
+
+	a := formatCursor(9)
+	b := formatCursor(10)
+	assert.Less(t, a, b, "lexicographic order must match numeric order")
+}