diff --git a/src/sender/verifier.rs b/src/sender/verifier.rs
index afecf56..29ebcb4 100644
--- a/src/sender/verifier.rs
+++ b/src/sender/verifier.rs
@@ -13,7 +13,21 @@ use {
 
 #[derive(Debug)]
 /// A verifier is used to verify certificates sent by the receiving server
-/// during the tls handshake.
+/// during the tls handshake. For convenience the [CertificateStore] trait
+/// is implemented for [std::collections::HashMap<String, String>] and
+/// [std::collections::BTreeMap<String, String>], so a Verifier can easily
+/// be constructed from those types.
+///
+/// This type is passed to [rustls::client::DangerousClientConfig::set_certificate_verifier]
+/// in order to allow Tofu certificate validation.
+/// # Examples
+/// Create a Verifier from a HashMap
+/// ```
+/// use std::collections::HashMap;
+/// use dory::prelude::{CertificateStore, Verifier};
+///
+/// let verifier: Verifier<HashMap<String, String>> = HashMap::new().into();
+/// ```
 pub struct Verifier<S: CertificateStore> {
     /// An item which serves as storage for certificates
     pub store: Arc<Mutex<S>>,
@@ -86,6 +100,8 @@ mod tests {
     use super::*;
 
     const CERT: &[u8] = include_bytes!("../../test/certificates/gemini.example.org/cert.der");
+    const FP: &'static str =
+        include_str!("../../test/certificates/gemini.example.org/fingerprint.txt");
 
     #[test]
     fn tofu() {
@@ -93,7 +109,22 @@ mod tests {
         let cert = rustls::Certificate(CERT.into());
         let name = rustls::ServerName::try_from("gemini.example.org").unwrap();
         let now = time::SystemTime::now();
-        let mut scts: Vec<&[u8]> = vec![];
-        let res = verifier.verify_server_cert(&cert, &[], &name, &mut scts.iter(), &[], now);
+        let scts: Vec<&[u8]> = vec![];
+        let res =
+            verifier.verify_server_cert(&cert, &[], &name, &mut scts.iter().copied(), &[], now);
+        assert!(res.is_ok());
+    }
+
+    #[test]
+    fn verify_previously_trusted() {
+        let verifier: Verifier<HashMap<String, String>> =
+            HashMap::from([("gemini.example.org".to_string(), FP.to_string())]).into();
+        let cert = rustls::Certificate(CERT.into());
+        let name = rustls::ServerName::try_from("gemini.example.org").unwrap();
+        let now = time::SystemTime::now();
+        let scts: Vec<&[u8]> = vec![];
+        let res =
+            verifier.verify_server_cert(&cert, &[], &name, &mut scts.iter().copied(), &[], now);
+        assert!(res.is_ok());
     }
 }
diff --git a/test/certificates/gemini.example.org/fingerprint.txt b/test/certificates/gemini.example.org/fingerprint.txt
new file mode 100644
index 0000000..cdb7c9e
--- /dev/null
+++ b/test/certificates/gemini.example.org/fingerprint.txt
@@ -0,0 +1 @@
+018a3210fe625b380e2021c1c3a5a6b0092f105e9350b62b72b97b73206fee69
\ No newline at end of file