diff --git a/Cargo.lock b/Cargo.lock
index ce822cb..4531c2e 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -20,6 +20,15 @@ dependencies = [
  "version_check",
 ]
 
+[[package]]
+name = "aho-corasick"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "67fc08ce920c31afb70f013dcce1bfc3a3195de6a228474e45e1f145b36f8d04"
+dependencies = [
+ "memchr",
+]
+
 [[package]]
 name = "arc-swap"
 version = "1.6.0"
@@ -284,6 +293,12 @@ version = "2.3.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "23d8666cb01533c39dde32bcbab8e227b4ed6679b2c925eba05feabea39508fb"
 
+[[package]]
+name = "difflib"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6184e33543162437515c2e2b48714794e37845ec9851711914eec9d308f6ebe8"
+
 [[package]]
 name = "digest"
 version = "0.10.6"
@@ -305,6 +320,12 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "downcast"
+version = "0.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1435fa1053d8b2fbbe9be7e97eca7f33d37b28409959813daefc1446a14247f1"
+
 [[package]]
 name = "dunce"
 version = "1.0.4"
@@ -396,6 +417,15 @@ dependencies = [
  "miniz_oxide",
 ]
 
+[[package]]
+name = "float-cmp"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "98de4bbd547a563b716d8dfa9aad1cb19bfab00f4fa09a6a4ed21dbcf44ce9c4"
+dependencies = [
+ "num-traits",
+]
+
 [[package]]
 name = "fnv"
 version = "1.0.7"
@@ -411,6 +441,12 @@ dependencies = [
  "percent-encoding",
 ]
 
+[[package]]
+name = "fragile"
+version = "2.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6c2141d6d6c8512188a7891b4b01590a45f6dac67afb4f255c4124dbb86d4eaa"
+
 [[package]]
 name = "fuchsia-cprng"
 version = "0.1.1"
@@ -472,6 +508,7 @@ dependencies = [
  "clippy",
  "gix",
  "hex",
+ "mockall",
  "serde",
  "serde_json",
  "sha2",
@@ -1355,6 +1392,15 @@ version = "2.7.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "12b6ee2129af8d4fb011108c73d99a1b83a85977f23b82460c0ae2e25bb4b57f"
 
+[[package]]
+name = "itertools"
+version = "0.10.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b0fd2260e829bddf4cb6ea802289de2f86d6a7a690192fbe91b3f46e0f2c8473"
+dependencies = [
+ "either",
+]
+
 [[package]]
 name = "itoa"
 version = "1.0.6"
@@ -1521,6 +1567,33 @@ dependencies = [
  "windows-sys 0.45.0",
 ]
 
+[[package]]
+name = "mockall"
+version = "0.11.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4c84490118f2ee2d74570d114f3d0493cbf02790df303d2707606c3e14e07c96"
+dependencies = [
+ "cfg-if",
+ "downcast",
+ "fragile",
+ "lazy_static",
+ "mockall_derive",
+ "predicates",
+ "predicates-tree",
+]
+
+[[package]]
+name = "mockall_derive"
+version = "0.11.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "22ce75669015c4f47b289fd4d4f56e894e4c96003ffdf3ac51313126f94c6cbb"
+dependencies = [
+ "cfg-if",
+ "proc-macro2",
+ "quote",
+ "syn 1.0.109",
+]
+
 [[package]]
 name = "nibble_vec"
 version = "0.1.0"
@@ -1540,6 +1613,12 @@ dependencies = [
  "minimal-lexical",
 ]
 
+[[package]]
+name = "normalize-line-endings"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "61807f77802ff30975e01f4f071c8ba10c022052f98b3294119f3e615d13e5be"
+
 [[package]]
 name = "num-traits"
 version = "0.2.15"
@@ -1621,6 +1700,36 @@ version = "0.2.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5b40af805b3121feab8a3c29f04d8ad262fa8e0561883e7653e024ae4479e6de"
 
+[[package]]
+name = "predicates"
+version = "2.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "59230a63c37f3e18569bdb90e4a89cbf5bf8b06fea0b84e65ea10cc4df47addd"
+dependencies = [
+ "difflib",
+ "float-cmp",
+ "itertools",
+ "normalize-line-endings",
+ "predicates-core",
+ "regex",
+]
+
+[[package]]
+name = "predicates-core"
+version = "1.0.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b794032607612e7abeb4db69adb4e33590fa6cf1149e95fd7cb00e634b92f174"
+
+[[package]]
+name = "predicates-tree"
+version = "1.0.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "368ba315fb8c5052ab692e68a0eefec6ec57b23a36959c14496f0b0df2c0cecf"
+dependencies = [
+ "predicates-core",
+ "termtree",
+]
+
 [[package]]
 name = "proc-macro2"
 version = "1.0.56"
@@ -1789,12 +1898,29 @@ dependencies = [
  "rust-argon2",
 ]
 
+[[package]]
+name = "regex"
+version = "1.8.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "af83e617f331cc6ae2da5443c602dfa5af81e517212d9d611a5b3ba1777b5370"
+dependencies = [
+ "aho-corasick",
+ "memchr",
+ "regex-syntax",
+]
+
 [[package]]
 name = "regex-automata"
 version = "0.1.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6c230d73fb8d8c1b9c0b3135c5142a8acee3a0558fb8db5cf1cb65f8d7862132"
 
+[[package]]
+name = "regex-syntax"
+version = "0.7.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a5996294f19bd3aae0453a862ad728f60e6600695733dd5df01da90c54363a3c"
+
 [[package]]
 name = "remove_dir_all"
 version = "0.5.3"
@@ -2119,6 +2245,12 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "termtree"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3369f5ac52d5eb6ab48c6b4ffdc8efbcad6b89c765749064ba298f2c68a16a76"
+
 [[package]]
 name = "thiserror"
 version = "1.0.40"
diff --git a/Cargo.toml b/Cargo.toml
index c283887..41646fe 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -19,3 +19,4 @@ tempdir = "0.3.7"
 serde = { version = "1.0.162", features = [ "derive" ]}
 serde_json = "1.0.96"
 trust-dns-client = "0.22.0"
+mockall = "0.11.4"
diff --git a/src/domain/checker.rs b/src/domain/checker.rs
index 7747aad..a885e8f 100644
--- a/src/domain/checker.rs
+++ b/src/domain/checker.rs
@@ -5,6 +5,8 @@ use trust_dns_client::client::{Client, SyncClient};
 use trust_dns_client::rr::{DNSClass, Name, RData, RecordType};
 use trust_dns_client::udp::UdpClientConnection;
 
+use mockall::automock;
+
 #[derive(Debug)]
 pub enum NewDNSCheckerError {
     InvalidResolverAddress,
@@ -32,6 +34,7 @@ impl<E: Error + 'static> From<E> for CheckDomainError {
     }
 }
 
+#[automock]
 pub trait Checker {
     fn check_domain(&self, domain: &str, challenge_token: &str) -> Result<(), CheckDomainError>;
 }