diff --git a/Cargo.lock b/Cargo.lock
index e312933..d176d67 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -214,6 +214,7 @@ dependencies = [
  "serde_json",
  "sha2",
  "task-local-extensions",
+ "temp-env",
  "thiserror",
  "tokio",
  "tracing",
@@ -2082,6 +2083,15 @@ dependencies = [
  "pin-utils",
 ]
 
+[[package]]
+name = "temp-env"
+version = "0.3.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "96374855068f47402c3121c6eed88d29cb1de8f3ab27090e273e420bdabcf050"
+dependencies = [
+ "parking_lot",
+]
+
 [[package]]
 name = "termtree"
 version = "0.5.1"
diff --git a/Cargo.toml b/Cargo.toml
index dddcb92..0655833 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -24,12 +24,19 @@ rust_decimal = { version = "1.33", features = ["serde-float"] }
 async-trait = "0.1"
 dotenvy = "0.15"
 clap = { version = "4.4", features = ["derive", "env"] }
-reqwest = { version = "0.11", default-features = false, features = ["json", "multipart", "rustls-tls"] }
+reqwest = { version = "0.11", default-features = false, features = ["json", "rustls-tls"] }
 url = "2.5"
 wiremock = "0.5"
 tokio-test = "0.4"
- mockall = "0.11"
-  reqwest-middleware = "0.2"
-  hyper = { version = "0.14", features = ["full"] }
-  bytes = "1.0"
-  comfy-table = "7.1"
+mockall = "0.11"
+reqwest-middleware = "0.2"
+hyper = { version = "0.14", features = ["full"] }
+bytes = "1.0"
+comfy-table = "7.1"
+http = "0.2"
+task-local-extensions = "0.1"
+aes-gcm = "0.10"
+pbkdf2 = "0.12"
+rand = "0.8"
+sha2 = "0.10"
+temp-env = "0.3"
diff --git a/banks2ff/Cargo.toml b/banks2ff/Cargo.toml
index 5dd7ac9..53e7167 100644
--- a/banks2ff/Cargo.toml
+++ b/banks2ff/Cargo.toml
@@ -29,17 +29,18 @@ gocardless-client = { path = "../gocardless-client" }
 reqwest-middleware = { workspace = true }
 hyper = { workspace = true }
 bytes = { workspace = true }
-http = "0.2"
-task-local-extensions = "0.1"
+http = { workspace = true }
+task-local-extensions = { workspace = true }
 
 # Encryption dependencies
-aes-gcm = "0.10"
-pbkdf2 = "0.12"
-rand = "0.8"
-sha2 = "0.10"
+aes-gcm = { workspace = true }
+pbkdf2 = { workspace = true }
+rand = { workspace = true }
+sha2 = { workspace = true }
 
 # CLI formatting dependencies
 comfy-table = { workspace = true }
 
 [dev-dependencies]
 mockall = { workspace = true }
+temp-env = { workspace = true }
diff --git a/banks2ff/src/core/config.rs b/banks2ff/src/core/config.rs
index 98007b9..51b1fc1 100644
--- a/banks2ff/src/core/config.rs
+++ b/banks2ff/src/core/config.rs
@@ -105,128 +105,137 @@ impl LoggingConfig {
     }
 }
 
-    #[cfg(test)]
-    mod tests {
-        use super::*;
-        use std::env;
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use temp_env::with_vars;
 
     #[test]
     fn test_gocardless_config_from_env() {
-        env::set_var("GOCARDLESS_ID", "test-id");
-        env::set_var("GOCARDLESS_KEY", "test-key");
-        env::set_var("GOCARDLESS_URL", "https://test.example.com");
-
-        let config = GoCardlessConfig::from_env().unwrap();
-        assert_eq!(config.secret_id, "test-id");
-        assert_eq!(config.secret_key, "test-key");
-        assert_eq!(config.url, "https://test.example.com");
-
-        env::remove_var("GOCARDLESS_ID");
-        env::remove_var("GOCARDLESS_KEY");
-        env::remove_var("GOCARDLESS_URL");
+        with_vars(
+            [
+                ("GOCARDLESS_ID", Some("test-id")),
+                ("GOCARDLESS_KEY", Some("test-key")),
+                ("GOCARDLESS_URL", Some("https://test.example.com")),
+            ],
+            || {
+                let config = GoCardlessConfig::from_env().unwrap();
+                assert_eq!(config.secret_id, "test-id");
+                assert_eq!(config.secret_key, "test-key");
+                assert_eq!(config.url, "https://test.example.com");
+            },
+        );
     }
 
     #[test]
     fn test_gocardless_config_default_url() {
-        env::set_var("GOCARDLESS_ID", "test-id");
-        env::set_var("GOCARDLESS_KEY", "test-key");
-        env::remove_var("GOCARDLESS_URL");
-
-        let config = GoCardlessConfig::from_env().unwrap();
-        assert_eq!(config.url, "https://bankaccountdata.gocardless.com");
-
-        env::remove_var("GOCARDLESS_ID");
-        env::remove_var("GOCARDLESS_KEY");
+        with_vars(
+            [
+                ("GOCARDLESS_ID", Some("test-id")),
+                ("GOCARDLESS_KEY", Some("test-key")),
+                ("GOCARDLESS_URL", None),
+            ],
+            || {
+                let config = GoCardlessConfig::from_env().unwrap();
+                assert_eq!(config.url, "https://bankaccountdata.gocardless.com");
+            },
+        );
     }
 
     #[test]
     fn test_gocardless_config_missing_id() {
-        env::remove_var("GOCARDLESS_ID");
-        env::set_var("GOCARDLESS_KEY", "test-key");
-
-        let result = GoCardlessConfig::from_env();
-        assert!(result.is_err());
-
-        env::remove_var("GOCARDLESS_KEY");
+        with_vars(
+            [
+                ("GOCARDLESS_ID", None),
+                ("GOCARDLESS_KEY", Some("test-key")),
+            ],
+            || {
+                let result = GoCardlessConfig::from_env();
+                assert!(result.is_err());
+            },
+        );
     }
 
     #[test]
     fn test_firefly_config_from_env() {
-        env::set_var("FIREFLY_III_URL", "https://firefly.test.com");
-        env::set_var("FIREFLY_III_API_KEY", "test-api-key");
-
-        let config = FireflyConfig::from_env().unwrap();
-        assert_eq!(config.url, "https://firefly.test.com");
-        assert_eq!(config.api_key, "test-api-key");
-
-        env::remove_var("FIREFLY_III_URL");
-        env::remove_var("FIREFLY_III_API_KEY");
+        with_vars(
+            [
+                ("FIREFLY_III_URL", Some("https://firefly.test.com")),
+                ("FIREFLY_III_API_KEY", Some("test-api-key")),
+            ],
+            || {
+                let config = FireflyConfig::from_env().unwrap();
+                assert_eq!(config.url, "https://firefly.test.com");
+                assert_eq!(config.api_key, "test-api-key");
+            },
+        );
     }
 
     #[test]
     fn test_cache_config_from_env() {
-        env::set_var("BANKS2FF_CACHE_KEY", "test-cache-key");
-        env::set_var("BANKS2FF_CACHE_DIR", "/tmp/test-cache");
-
-        let config = CacheConfig::from_env().unwrap();
-        assert_eq!(config.key, "test-cache-key");
-        assert_eq!(config.directory, "/tmp/test-cache");
-
-        env::remove_var("BANKS2FF_CACHE_KEY");
-        env::remove_var("BANKS2FF_CACHE_DIR");
+        with_vars(
+            [
+                ("BANKS2FF_CACHE_KEY", Some("test-cache-key")),
+                ("BANKS2FF_CACHE_DIR", Some("/tmp/test-cache")),
+            ],
+            || {
+                let config = CacheConfig::from_env().unwrap();
+                assert_eq!(config.key, "test-cache-key");
+                assert_eq!(config.directory, "/tmp/test-cache");
+            },
+        );
     }
 
     #[test]
     fn test_cache_config_default_directory() {
-        env::remove_var("BANKS2FF_CACHE_DIR");
-        env::set_var("BANKS2FF_CACHE_KEY", "test-cache-key");
-
-        let config = CacheConfig::from_env().unwrap();
-        assert_eq!(config.directory, "data/cache");
-
-        env::remove_var("BANKS2FF_CACHE_KEY");
+        with_vars(
+            [
+                ("BANKS2FF_CACHE_DIR", None),
+                ("BANKS2FF_CACHE_KEY", Some("test-cache-key")),
+            ],
+            || {
+                let config = CacheConfig::from_env().unwrap();
+                assert_eq!(config.directory, "data/cache");
+            },
+        );
     }
 
     #[test]
     fn test_logging_config_from_env() {
-        env::set_var("RUST_LOG", "debug");
-
-        let config = LoggingConfig::from_env().unwrap();
-        assert_eq!(config.level, "debug");
-
-        env::remove_var("RUST_LOG");
+        with_vars([("RUST_LOG", Some("debug"))], || {
+            let config = LoggingConfig::from_env().unwrap();
+            assert_eq!(config.level, "debug");
+        });
     }
 
     #[test]
     fn test_logging_config_default() {
-        env::remove_var("RUST_LOG");
-
-        let config = LoggingConfig::from_env().unwrap();
-        assert_eq!(config.level, "warn");
+        with_vars([("RUST_LOG", None::<&str>)], || {
+            let config = LoggingConfig::from_env().unwrap();
+            assert_eq!(config.level, "warn");
+        });
     }
 
     #[test]
     fn test_full_config_from_env() {
-        env::set_var("GOCARDLESS_ID", "test-id");
-        env::set_var("GOCARDLESS_KEY", "test-key");
-        env::set_var("FIREFLY_III_URL", "https://firefly.test.com");
-        env::set_var("FIREFLY_III_API_KEY", "test-api-key");
-        env::set_var("BANKS2FF_CACHE_KEY", "test-cache-key");
-        env::set_var("RUST_LOG", "info");
-
-        let config = Config::from_env().unwrap();
-        assert_eq!(config.gocardless.secret_id, "test-id");
-        assert_eq!(config.gocardless.secret_key, "test-key");
-        assert_eq!(config.firefly.url, "https://firefly.test.com");
-        assert_eq!(config.firefly.api_key, "test-api-key");
-        assert_eq!(config.cache.key, "test-cache-key");
-        assert_eq!(config.logging.level, "info");
-
-        env::remove_var("GOCARDLESS_ID");
-        env::remove_var("GOCARDLESS_KEY");
-        env::remove_var("FIREFLY_III_URL");
-        env::remove_var("FIREFLY_III_API_KEY");
-        env::remove_var("BANKS2FF_CACHE_KEY");
-        env::remove_var("RUST_LOG");
+        with_vars(
+            [
+                ("GOCARDLESS_ID", Some("test-id")),
+                ("GOCARDLESS_KEY", Some("test-key")),
+                ("FIREFLY_III_URL", Some("https://firefly.test.com")),
+                ("FIREFLY_III_API_KEY", Some("test-api-key")),
+                ("BANKS2FF_CACHE_KEY", Some("test-cache-key")),
+                ("RUST_LOG", Some("info")),
+            ],
+            || {
+                let config = Config::from_env().unwrap();
+                assert_eq!(config.gocardless.secret_id, "test-id");
+                assert_eq!(config.gocardless.secret_key, "test-key");
+                assert_eq!(config.firefly.url, "https://firefly.test.com");
+                assert_eq!(config.firefly.api_key, "test-api-key");
+                assert_eq!(config.cache.key, "test-cache-key");
+                assert_eq!(config.logging.level, "info");
+            },
+        );
     }
 }