diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..a6c57f5
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+*.json
diff --git a/arxiva.go b/arxiva.go
index a019b05..ba4266e 100644
--- a/arxiva.go
+++ b/arxiva.go
@@ -11,6 +11,8 @@ import (
 	"time"
 )
 
+var httpClient = &http.Client{}
+
 type Paper struct {
 	Title    string `json:"title"`
 	Abstract string `json:"abstract"`
@@ -63,7 +65,11 @@ func FetchPapers(startDate string, endDate string, query string, maxPapers int)
 	params.Add("search_query", searchQuery)
 	params.Add("max_results", fmt.Sprintf("%d", maxPapers))
 
-	resp, err := http.Get(baseURL + "?" + params.Encode())
+	req, err := http.NewRequest("GET", baseURL+"?"+params.Encode(), nil)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create request: %v", err)
+	}
+	resp, err := httpClient.Do(req)
 	if err != nil {
 		return nil, fmt.Errorf("failed to fetch from arXiv: %v", err)
 	}
@@ -93,6 +99,10 @@ func FetchPapers(startDate string, endDate string, query string, maxPapers int)
 }
 
 func SaveToFile(papers []Paper, startDate string, endDate string, query string) error {
+	if len(papers) == 0 {
+		return fmt.Errorf("no papers to save")
+	}
+
 	filename := fmt.Sprintf("%s-%s-%s.json", startDate, endDate, SanitizeFilename(query))
 
 	data, err := json.MarshalIndent(papers, "", "  ")
diff --git a/arxiva_test.go b/arxiva_test.go
new file mode 100644
index 0000000..25a1070
--- /dev/null
+++ b/arxiva_test.go
@@ -0,0 +1,173 @@
+package arxiva
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"io"
+	"net/http"
+	"os"
+	"testing"
+)
+
+// Mock HTTP client that implements the http.RoundTripper interface
+type mockTransport struct {
+	response *http.Response
+	err      error
+}
+
+func (m *mockTransport) RoundTrip(req *http.Request) (*http.Response, error) {
+	return m.response, m.err
+}
+
+func TestFetchPapers(t *testing.T) {
+	tests := []struct {
+		name         string
+		mockResponse string
+		mockError    error
+		expectError  bool
+	}{
+		{
+			name: "successful fetch",
+			mockResponse: `<?xml version="1.0" encoding="UTF-8"?>
+<feed xmlns="http://www.w3.org/2005/Atom">
+  <entry>
+    <title>Test Paper</title>
+    <summary>Test summary</summary>
+    <id>http://arxiv.org/abs/1234.56789</id>
+  </entry>
+</feed>`,
+			expectError: false,
+		},
+		{
+			name:        "api error",
+			mockError:   errors.New("API unavailable"),
+			expectError: true,
+		},
+		{
+			name:         "invalid json",
+			mockResponse: "invalid json",
+			expectError:  true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			// Setup mock HTTP client
+			var client *http.Client
+			var response *http.Response
+			if tt.mockError == nil {
+				response = &http.Response{
+					StatusCode: http.StatusOK,
+					Body:       io.NopCloser(bytes.NewBufferString(tt.mockResponse)),
+				}
+			}
+			client = &http.Client{
+				Transport: &mockTransport{
+					response: response,
+					err:      tt.mockError,
+				},
+			}
+
+			// Replace default client with mock
+			originalClient := httpClient
+			httpClient = client
+			defer func() { httpClient = originalClient }()
+
+			// Test function
+			papers, err := FetchPapers("20240101", "20240125", "test", 1)
+			if err != nil {
+				t.Logf("FetchPapers error: %v", err)
+			}
+			if (err != nil) != tt.expectError {
+				t.Errorf("FetchPapers() error = %v, expectError %v", err, tt.expectError)
+				return
+			}
+
+			if !tt.expectError && len(papers) == 0 {
+				t.Error("Expected papers but got none")
+			}
+		})
+	}
+}
+
+func TestSaveToFile(t *testing.T) {
+	tests := []struct {
+		name        string
+		papers      []Paper
+		expectError bool
+	}{
+		{
+			name: "successful save",
+			papers: []Paper{
+				{
+					Title:    "Test Paper",
+					Abstract: "Test abstract",
+					ArxivID:  "1234.56789",
+				},
+			},
+			expectError: false,
+		},
+		{
+			name:        "empty papers",
+			papers:      []Paper{},
+			expectError: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			// Create temp file
+			tmpFile, err := os.CreateTemp("", "test-*.json")
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer os.Remove(tmpFile.Name())
+
+			// Test function
+			filename := "20240101-20240125-test.json"
+			err = SaveToFile(tt.papers, "20240101", "20240125", "test")
+			if err != nil && !tt.expectError {
+				t.Errorf("SaveToFile() unexpected error: %v", err)
+				return
+			}
+			if err == nil && tt.expectError {
+				t.Errorf("SaveToFile() expected error but got none")
+				return
+			}
+			if tt.expectError {
+				return
+			}
+
+			// Clean up test file
+			defer os.Remove(filename)
+			if (err != nil) != tt.expectError {
+				t.Errorf("SaveToFile() error = %v, expectError %v", err, tt.expectError)
+				return
+			}
+
+			// Verify file contents if successful
+			if !tt.expectError {
+				var savedPapers []Paper
+				fileData, err := os.ReadFile(filename)
+				if err != nil {
+					t.Errorf("Failed to read saved file: %v", err)
+					return
+				}
+
+				if err := json.Unmarshal(fileData, &savedPapers); err != nil {
+					t.Errorf("Failed to unmarshal saved file: %v", err)
+					return
+				}
+
+				if len(savedPapers) != len(tt.papers) {
+					t.Errorf("Expected %d papers, got %d", len(tt.papers), len(savedPapers))
+				}
+			} else if tt.name == "empty papers" {
+				if _, err := os.Stat(filename); !os.IsNotExist(err) {
+					t.Errorf("File should not exist for empty papers case")
+				}
+			}
+		})
+	}
+}