added test files

cmd/app/handler/httpjson/health_test.go

@@ -0,0 +1,35 @@
+package httpjson
+
+import (
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"go.uber.org/zap"
+)
+
+func TestHealthCheck(t *testing.T) {
+	e, _ := New(zap.NewNop())
+
+	req := httptest.NewRequest(http.MethodGet, "/health", nil)
+	rec := httptest.NewRecorder()
+
+	e.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Errorf("status = %d, want %d", rec.Code, http.StatusOK)
+	}
+
+	body, err := io.ReadAll(rec.Body)
+	if err != nil {
+		t.Fatalf("read body: %v", err)
+	}
+	if string(body) != "OK" {
+		t.Errorf("body = %q, want %q", body, "OK")
+	}
+
+	if ct := rec.Header().Get("Content-Type"); ct != "text/plain; charset=UTF-8" {
+		t.Errorf("Content-Type = %q, want text/plain; charset=UTF-8", ct)
+	}
+}