diff --git a/app/gitignore-gen/tests/unit/combine_tests.rs b/app/gitignore-gen/tests/unit/combine_tests.rs
new file mode 100644
index 0000000..6872735
--- /dev/null
+++ b/app/gitignore-gen/tests/unit/combine_tests.rs
@@ -0,0 +1,207 @@
+use crate::templates::TemplateLoader;
+
+#[cfg(test)]
+mod combine_tests {
+    use super::*;
+
+    #[test]
+    fn test_combine_removes_duplicates() {
+        let loader = TemplateLoader::new(None);
+
+        let result1 = loader.combine_templates(&["rust"]);
+        assert!(result1.is_ok());
+
+        let result2 = loader.combine_templates(&["rust", "rust"]);
+        assert!(result2.is_ok());
+
+        let count1 = result1.unwrap().lines().filter(|l| !l.starts_with("#")).count();
+        let count2 = result2.unwrap().lines().filter(|l| !l.starts_with("#")).count();
+
+        assert_eq!(count1, count2);
+    }
+
+    #[test]
+    fn test_combine_preserves_unique_patterns() {
+        let loader = TemplateLoader::new(None);
+
+        let rust_result = loader.combine_templates(&["rust"]);
+        let python_result = loader.combine_templates(&["python"]);
+        let combined = loader.combine_templates(&["rust", "python"]);
+
+        assert!(combined.is_ok());
+
+        let combined_content = combined.unwrap();
+
+        assert!(combined_content.contains("# Generated by gitignore-gen"));
+        assert!(combined_content.contains("rust") || combined_content.contains("python"));
+    }
+
+    #[test]
+    fn test_combine_multiple_templates() {
+        let loader = TemplateLoader::new(None);
+
+        let templates = ["rust", "python", "go"];
+        let result = loader.combine_templates(&templates);
+
+        assert!(result.is_ok());
+        let content = result.unwrap();
+        assert!(!content.is_empty());
+    }
+
+    #[test]
+    fn test_combine_with_nonexistent_template() {
+        let loader = TemplateLoader::new(None);
+
+        let result = loader.combine_templates(&["rust", "nonexistent_template"]);
+        assert!(result.is_ok());
+    }
+
+    #[test]
+    fn test_combine_empty_list() {
+        let loader = TemplateLoader::new(None);
+
+        let result = loader.combine_templates(&[]);
+        assert!(result.is_ok());
+        let content = result.unwrap();
+        assert!(content.contains("Combined templates:"));
+    }
+
+    #[test]
+    fn test_combine_order() {
+        let loader = TemplateLoader::new(None);
+
+        let rust_result = loader.combine_templates(&["rust"]);
+        let python_result = loader.combine_templates(&["python"]);
+        let combined = loader.combine_templates(&["rust", "python"]);
+
+        assert!(combined.is_ok());
+        let combined_content = combined.unwrap();
+
+        assert!(rust_result.unwrap().len() > 0);
+        assert!(python_result.unwrap().len() > 0);
+        assert!(combined_content.len() >= rust_result.unwrap().len());
+    }
+
+    #[test]
+    fn test_combine_header_format() {
+        let loader = TemplateLoader::new(None);
+
+        let result = loader.combine_templates(&["rust", "python", "go"]);
+        assert!(result.is_ok());
+
+        let content = result.unwrap();
+        let lines: Vec<&str> = content.lines().collect();
+
+        assert_eq!(lines[0], "# Generated by gitignore-gen");
+        assert!(lines[1].starts_with("# Combined templates:"));
+    }
+
+    #[test]
+    fn test_combine_pattern_deduplication_across_templates() {
+        let loader = TemplateLoader::new(None);
+
+        let rust_templates = loader.get_template("rust");
+        let python_templates = loader.get_template("python");
+
+        assert!(rust_templates.is_some());
+        assert!(python_templates.is_some());
+
+        let combined = loader.combine_templates(&["rust", "python"]);
+        assert!(combined.is_ok());
+
+        let content = combined.unwrap();
+        let lines: Vec<&str> = content.lines().collect();
+        let pattern_lines: Vec<&str> = lines
+            .iter()
+            .filter(|l| !l.starts_with("#"))
+            .filter(|l| !l.is_empty())
+            .cloned()
+            .collect();
+
+        let unique_patterns: std::collections::HashSet<&str> =
+            pattern_lines.iter().cloned().collect();
+
+        assert_eq!(pattern_lines.len(), unique_patterns.len());
+    }
+}
+
+#[cfg(test)]
+mod pattern_tests {
+    use super::*;
+
+    #[test]
+    fn test_pattern_format_valid() {
+        let valid_patterns = [
+            "*.log",
+            "target/",
+            ".env",
+            "/build",
+            "*.py[cod]",
+            "!.gitignore",
+        ];
+
+        for pattern in valid_patterns {
+            assert!(!pattern.is_empty());
+        }
+    }
+
+    #[test]
+    fn test_pattern_with_directory() {
+        let loader = TemplateLoader::new(None);
+        let rust_template = loader.get_template("rust");
+
+        assert!(rust_template.is_some());
+
+        let patterns = &rust_template.unwrap().patterns;
+        let has_target = patterns.iter().any(|p| p.contains("target"));
+        assert!(has_target);
+    }
+
+    #[test]
+    fn test_pattern_with_wildcard() {
+        let loader = TemplateLoader::new(None);
+        let python_template = loader.get_template("python");
+
+        assert!(python_template.is_some());
+
+        let patterns = &python_template.unwrap().patterns;
+        let has_wildcard = patterns.iter().any(|p| p.contains('*'));
+        assert!(has_wildcard);
+    }
+}
+
+#[cfg(test)]
+mod edge_case_tests {
+    use super::*;
+
+    #[test]
+    fn test_combine_very_large_list() {
+        let loader = TemplateLoader::new(None);
+        let templates = loader.list_templates();
+        let result = loader.combine_templates(&templates);
+        assert!(result.is_ok());
+    }
+
+    #[test]
+    fn test_search_results_sorted() {
+        let loader = TemplateLoader::new(None);
+
+        let results = loader.search_templates("");
+
+        for i in 0..results.len().saturating_sub(1) {
+            assert!(results[i] <= results[i + 1]);
+        }
+    }
+
+    #[test]
+    fn test_all_embedded_templates_loadable() {
+        let loader = TemplateLoader::new(None);
+        let templates = loader.list_templates();
+
+        for name in templates {
+            let template = loader.get_template(name);
+            assert!(template.is_some());
+            assert_eq!(template.unwrap().name, name);
+        }
+    }
+}