diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..14dc81f
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,40 @@
+use http::Uri;
+use rust_util::*;
+
+pub fn make_url(base_url: &str, ts_url: &str) -> XResult<String> {
+    let lower_ts_url = ts_url.to_lowercase();
+    if lower_ts_url.starts_with("http://") || lower_ts_url.starts_with("https://") {
+        return Ok(ts_url.into());
+    }
+
+    let parsed_base_url = base_url.parse::<Uri>()?;
+    let lower_scheme_str = match parsed_base_url.scheme_str() {
+        None => return Err(new_box_error(&format!("Base url has no scheme: {}", base_url))),
+        Some(s) => s.to_lowercase(),
+    };
+
+    if ts_url.starts_with("//") {
+        return Ok(iff!(lower_scheme_str == "http", "http:", "https:").to_owned() + ts_url);
+    }
+
+    let authority = match parsed_base_url.authority() {
+        None => return Err(new_box_error(&format!("Base url has no authority: {}", base_url))),
+        Some(a) => a,
+    };
+
+    if ts_url.starts_with('/') {
+        return Ok(format!("{}://{}{}", lower_scheme_str, authority, ts_url));
+    }
+
+    let relative_base_url = format!("{}://{}{}", lower_scheme_str, authority, parsed_base_url.path());
+    if relative_base_url.ends_with('/') {
+        // ends with '/'
+        Ok(relative_base_url + ts_url)
+    } else {
+        // not ends with '/'
+        let mut splited_by_slash = relative_base_url.split('/').collect::<Vec<_>>();
+        let splited_by_slash_len = splited_by_slash.len();
+        splited_by_slash[splited_by_slash_len - 1] = ts_url;        
+        Ok(splited_by_slash.join("/"))
+    }
+}
diff --git a/src/main.rs b/src/main.rs
index 62f7193..bb4cbcf 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,5 +1,4 @@
 use http::Uri;
-use rust_util::*;
 
 fn main() {
     println!("Hello, world!");
@@ -22,42 +21,6 @@ fn main() {
         v[l]="xxxxx";
     }
     println!("{:?}", v.join("/"));
-}
-
-fn _make_url(base_url: &str, ts_url: &str) -> XResult<String> {
-    let lower_ts_url = ts_url.to_lowercase();
-    if lower_ts_url.starts_with("http://") || lower_ts_url.starts_with("https://") {
-        return Ok(ts_url.into());
-    }
-
-    let parsed_base_url = base_url.parse::<Uri>()?;
-    let lower_scheme_str = match parsed_base_url.scheme_str() {
-        None => return Err(new_box_error(&format!("Base url has no scheme: {}", base_url))),
-        Some(s) => s.to_lowercase(),
-    };
-
-    if ts_url.starts_with("//") {
-        return Ok(iff!(lower_scheme_str == "http", "http:", "https:").to_owned() + ts_url);
-    }
-
-    let authority = match parsed_base_url.authority() {
-        None => return Err(new_box_error(&format!("Base url has no authority: {}", base_url))),
-        Some(a) => a,
-    };
-
-    if ts_url.starts_with('/') {
-        return Ok(format!("{}://{}{}", lower_scheme_str, authority, ts_url));
-    }
-
-    let relative_base_url = format!("{}://{}{}", lower_scheme_str, authority, parsed_base_url.path());
-    if relative_base_url.ends_with('/') {
-        // ends with '/'
-        Ok(relative_base_url + ts_url)
-    } else {
-        // not ends with '/'
-        let mut splited_by_slash = relative_base_url.split('/').collect::<Vec<_>>();
-        let splited_by_slash_len = splited_by_slash.len();
-        splited_by_slash[splited_by_slash_len - 1] = ts_url;        
-        Ok(splited_by_slash.join("/"))
-    }
+
+    // make_url("", "").ok();
 }
diff --git a/tests/test_make_url.rs b/tests/test_make_url.rs
new file mode 100644
index 0000000..21b4e7a
--- /dev/null
+++ b/tests/test_make_url.rs
@@ -0,0 +1,16 @@
+use m3u8download::make_url;
+
+#[test]
+fn test_make_url() {
+    assert_eq!("http://example.com/a/b.ts", &make_url("", "http://example.com/a/b.ts").unwrap());
+    assert_eq!("https://example.com/a/b.ts", &make_url("", "https://example.com/a/b.ts").unwrap());
+    assert_eq!("http://example.com/a/b.ts", &make_url("HTTP://example.com/x/y.m3u8", "//example.com/a/b.ts").unwrap());
+    assert_eq!("http://example.com/a/b.ts", &make_url("http://example.com/x/y.m3u8", "//example.com/a/b.ts").unwrap());
+    assert_eq!("https://example.com/a/b.ts", &make_url("HTTPS://example.com/x/y.m3u8", "//example.com/a/b.ts").unwrap());
+    assert_eq!("https://example.com/a/b.ts", &make_url("https://example.com/x/y.m3u8", "//example.com/a/b.ts").unwrap());
+    assert_eq!("https://example.com/a/b.ts", &make_url("https://example.com/x/y.m3u8", "/a/b.ts").unwrap());
+    assert_eq!("https://example.com/x/b.ts", &make_url("https://example.com/x/y.m3u8", "b.ts").unwrap());
+    assert_eq!("https://example.com/x/b.ts", &make_url("https://example.com/x/y", "b.ts").unwrap());
+    assert_eq!("https://example.com/x/y/b.ts", &make_url("https://example.com/x/y/", "b.ts").unwrap());
+    assert_eq!("https://example.com/x/y/a/b.ts", &make_url("https://example.com/x/y/", "a/b.ts").unwrap());
+}