diff --git a/CHANGELOG.md b/CHANGELOG.md
index 62615bc..470cf0a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## Unreleased
+
+- Support passing `:test_mode` parameter into `options` hash for all CRUD operations.
+
 ## 1.0.0 (2023-11-27)
 
 - Interact with the Payrix API!
diff --git a/README.md b/README.md
index 066c05c..f11c787 100644
--- a/README.md
+++ b/README.md
@@ -240,10 +240,13 @@ merchant.members # => [...}
 
 #### Per Request Configuration
 
-Pass in `:api_key` to set the API key used per request.
+Set the following configuration parameters per request.
+
+- `:api_key` - Set the API key used.
+- `:test_mode` - Set `true` to use the Sandvox environment, and `false` to use the Production environment.
 
 ```ruby
-Payrix::Merchant.retrieve('t1_mer_620acd189522582b3fb7849', { api_key: 'b442...' })
+Payrix::Merchant.retrieve('t1_mer_620acd189522582b3fb7849', { api_key: 'b442...', test_mode: true })
 ```
 
 This is useful if you need to set the API key in a thread-safe way, which is not possible through
diff --git a/lib/payrix/client.rb b/lib/payrix/client.rb
index 526d031..3110c5d 100644
--- a/lib/payrix/client.rb
+++ b/lib/payrix/client.rb
@@ -4,7 +4,7 @@ module Payrix
   # The Payrix::Client is used both internally and externally to initiate API requests to the Payrix API.
   class Client
     def request(method:, resource:, data: {}, filters: {}, options: {})
-      url = Payrix.configuration.url
+      url = Payrix.configuration.url(options[:test_mode])
 
       page_number = Payrix::RequestOptions::Page::Number.construct(options[:page])
       page_limit = Payrix::RequestOptions::Page::Limit.construct(options[:limit])
diff --git a/spec/lib/payrix/client_spec.rb b/spec/lib/payrix/client_spec.rb
index b8875be..835f1c1 100644
--- a/spec/lib/payrix/client_spec.rb
+++ b/spec/lib/payrix/client_spec.rb
@@ -37,7 +37,7 @@
           WebMock
             .stub_request(
               :get,
-              'https://api.payrix.com/txns?page[number]=1&page[limit]=10&expand[merchant][]=',
+              'https://test-api.payrix.com/txns?page[number]=1&page[limit]=10&expand[merchant][]=',
             )
             .with(
               headers: {
@@ -68,6 +68,7 @@
                 limit: 10,
                 expand: ['merchant'],
                 api_key: 'custom-key',
+                test_mode: true,
               },
             )
 
@@ -110,7 +111,7 @@
       it 'supports advanced requests' do
         stub =
           WebMock
-            .stub_request(:post, 'https://api.payrix.com/txns?expand[merchant][]=')
+            .stub_request(:post, 'https://test-api.payrix.com/txns?expand[merchant][]=')
             .with(
               headers: {
                 'Content-Type' => 'application/json',
@@ -142,6 +143,7 @@
               options: {
                 expand: ['merchant'],
                 api_key: 'custom-key',
+                test_mode: true,
               },
             )
 
@@ -192,7 +194,7 @@
       it 'supports advanced requests' do
         stub =
           WebMock
-            .stub_request(:put, 'https://api.payrix.com/txns/t1_txn_64026b07cc6a79dd5cfd0da')
+            .stub_request(:put, 'https://test-api.payrix.com/txns/t1_txn_64026b07cc6a79dd5cfd0da')
             .with(
               headers: {
                 'Content-Type' => 'application/json',
@@ -223,6 +225,7 @@
               },
               options: {
                 api_key: 'custom-key',
+                test_mode: true,
               },
             )
 
@@ -261,7 +264,7 @@
       it 'supports advanced requests' do
         stub =
           WebMock
-            .stub_request(:delete, 'https://api.payrix.com/txns/t1_txn_64026b07cc6a79dd5cfd0da')
+            .stub_request(:delete, 'https://test-api.payrix.com/txns/t1_txn_64026b07cc6a79dd5cfd0da')
             .with(
               headers: {
                 'Content-Type' => 'application/json',
@@ -286,6 +289,7 @@
               resource: 'txns/t1_txn_64026b07cc6a79dd5cfd0da',
               options: {
                 api_key: 'custom-key',
+                test_mode: true,
               },
             )