diff --git a/src/file/checked.rs b/src/file/checked.rs
index accef63..b7118d6 100644
--- a/src/file/checked.rs
+++ b/src/file/checked.rs
@@ -112,3 +112,83 @@ impl FileTrait for Checked {
         super::check_hash(&self.path, self.size, self.hash.as_deref(), on_progress)
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use tempfile::TempDir;
+
+    use crate::{
+        create_file,
+        file::tests::{CASES, HASHES},
+    };
+
+    use super::*;
+
+    #[test]
+    fn new_on_existing_file_works() {
+        for (content, size) in CASES {
+            let file = create_file(content);
+            let path = file
+                .path()
+                .canonicalize()
+                .expect("the file should have a canonical path");
+
+            let chk = Checked::new(file.path()).expect("creating `Checked` should succeed");
+            assert_eq!(chk.path, path);
+            assert_eq!(chk.size, size);
+            assert!(chk.hash.is_none());
+        }
+    }
+
+    #[test]
+    fn new_on_dir_errors() {
+        let tempdir = TempDir::new().expect("creating temp dir");
+        let fs_root = PathBuf::from("/");
+
+        let dirs = [tempdir.path(), fs_root.as_path()];
+
+        for p in dirs {
+            let err = Checked::new(p).expect_err("creating `Checked` should fail");
+            assert_eq!(err.kind(), io::ErrorKind::InvalidInput);
+            #[cfg(target_os = "linux")]
+            assert_eq!(err.to_string(), "Not a regular file");
+        }
+    }
+
+    #[test]
+    fn new_on_nex_errors() {
+        let tempdir = TempDir::new().expect("creating temp dir");
+        let nex_paths = [0, 1, 2, 3, 4].map(|i| tempdir.path().join(format!("nex_{i}.ext")));
+
+        for p in nex_paths {
+            let err = Checked::new(p).expect_err("creating `Checked` should fail");
+            assert_eq!(err.kind(), io::ErrorKind::NotFound);
+            #[cfg(target_os = "linux")]
+            assert_eq!(err.to_string(), "No such file or directory (os error 2)");
+        }
+    }
+
+    #[test]
+    fn hashing_works() {
+        for (&(content, _), hash) in CASES.iter().zip(HASHES) {
+            let file = create_file(content);
+            let mut chk = Checked::new(file.path()).expect("creating `Checked` should succeed");
+
+            chk.hash(drop).expect("hashing should succeed");
+            assert_eq!(chk.hash, Some(hash.to_string()));
+        }
+    }
+
+    #[test]
+    fn hashing_again_errors() {
+        for (content, _) in CASES {
+            let file = create_file(content);
+            let mut chk = Checked::new(file.path()).expect("creating `Checked` should succeed");
+
+            chk.hash(drop).expect("hashing should succeed");
+            let err = chk.hash(drop).expect_err("hashing twice should fail");
+
+            assert!(err.is_mismatch("unhashed file", chk.path.display().to_string()));
+        }
+    }
+}
diff --git a/src/file/mod.rs b/src/file/mod.rs
index f61845a..b8dd45b 100644
--- a/src/file/mod.rs
+++ b/src/file/mod.rs
@@ -124,20 +124,11 @@ pub trait FileTrait {
 
 #[cfg(test)]
 mod tests {
-    use std::io::Write;
-
-    use tempfile::NamedTempFile;
+    use crate::create_file;
 
     use super::*;
 
-    /// Helper to create a temp file from `data`
-    fn create_file(data: &[u8]) -> NamedTempFile {
-        let mut tmp = NamedTempFile::new().expect("creating temp file");
-        tmp.write_all(data).expect("writing to tempfile");
-        tmp
-    }
-
-    static CASES: [(&[u8], u64); 8] = [
+    pub static CASES: [(&[u8], u64); 8] = [
         (b"The quick brown fox jumps over the lazy dog", 43), // common pangram
         (b"hello world", 11),                                 // simple greeting
         (b"", 0),                                             // empty slice
@@ -148,7 +139,7 @@ mod tests {
         (b"foo\0bar\0baz", 11),                               // embedded nulls
     ];
 
-    static HASHES: [&str; 8] = [
+    pub static HASHES: [&str; 8] = [
         "qK3Uvd39k+SHfSdG5igXsRY2Sh+nvBSNlQkLxzM7NnP4JAHPeqLkyx7NkCluPxTLVBP47Xe+cwRbE5FM3NapGA", // common pangram
         "Ahzth5kpbOylV4MquUGlC0oR+DR4zxQfUfkz9lOrn7zAWgN83b7QbjCb8zSULE5YzfGkbiN5EczX/Pl4fLx/0A", // simple greeting
         "eGoC90IBWQPGxv2FJVLScpEvR0DhWEdhiobiF/cfVBnSXhAxr+5YUxOJZESTTrBLkDpoWxRIt1XVb3Aa/pvizg", // empty slice
@@ -162,8 +153,9 @@ mod tests {
     #[test]
     fn compute_hash_as_expected() {
         for (&(content, size), expected_hash) in CASES.iter().zip(HASHES) {
-            // to capture progress updates from `compute_hash`
             let file = create_file(content);
+
+            // to capture progress updates from `compute_hash`
             let mut read_total = 0;
             let callback = |n| read_total += n;
 
diff --git a/src/lib.rs b/src/lib.rs
index 4e979e7..2efbcd5 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -15,7 +15,6 @@ pub use cli::Cli;
 pub use error::{Error, Parameter, Result};
 
 #[cfg(test)]
-#[inline]
 pub fn check_trait<E, A>(expected: &E, actual: &A, tr: &'static str, ty: &'static str)
 where
     E: std::fmt::Debug + PartialEq<A>,
@@ -26,3 +25,13 @@ where
         "`impl {tr} for {ty}` expected: {expected:?}, actual: {actual:?}",
     );
 }
+
+/// Helper to create a temp file from `data`
+#[cfg(test)]
+fn create_file(data: &[u8]) -> tempfile::NamedTempFile {
+    use std::io::Write;
+
+    let mut tmp = tempfile::NamedTempFile::new().expect("creating temp file");
+    tmp.write_all(data).expect("writing to tempfile");
+    tmp
+}