diff --git a/project.clj b/project.clj
index 4991158..0f0b197 100644
--- a/project.clj
+++ b/project.clj
@@ -8,5 +8,7 @@
 
   :profiles {:dev {:plugins [[lein-cloverage "1.0.10"]
                              [lein-kibit "0.1.6"]
-                             [jonase/eastwood "0.2.5"]]
-                   :dependencies [[org.clojure/clojure "1.9.0"]]}})
+                             [jonase/eastwood "0.2.5"]
+                             [lein-eftest "0.5.2"]]
+                   :dependencies [[org.clojure/clojure "1.9.0"]
+                                  [funcool/struct "1.3.0"]]}})
diff --git a/src/rop/core.clj b/src/rop/core.clj
index 2eb2242..da1610f 100644
--- a/src/rop/core.clj
+++ b/src/rop/core.clj
@@ -83,3 +83,30 @@
        :status (get-in extracted-result [:response :status] 200)
        :headers (get-in extracted-result [:response :headers] {})}
       extracted-result)))
+
+
+(defn =validate-request=
+  "A railway function that validates a request by a given scheme.
+   If data are valid it updates them in the request (with coerced data), otherwise returns Bad Requests within errors.
+
+   Parameters:
+     - `validate` a function that takes an input and a validation scheme, it should return a tuple of errors
+          and validated input
+     - `scheme` a validation scheme
+     - `default` default values as a `hash-map`, it will be merged into a validated input
+     - `request-key a key in a `request` that holds the input data`
+     - `input` a ROP input"
+  [validate scheme defaults request-key {:keys [request] :as input}]
+  (let [[errors validated-input] (validate (select-keys (get request request-key) (keys scheme)) scheme)]
+    (if (nil? errors)
+      (succeed (assoc-in input [:request request-key] (merge (zipmap (keys scheme) (repeat nil))
+                                                             defaults
+                                                             validated-input)))
+      (fail {:status 400, :body {:errors errors}}))))
+
+
+(defn =merge-params=
+  "A railway function that merges a given `source` key into a `target` key in a request.
+   It's useful when route params and body params are validated together."
+  [source target {:keys [request] :as input}]
+  (succeed (update-in input [:request target] merge (get request source))))
diff --git a/test/rop/core_test.clj b/test/rop/core_test.clj
index 5a755fc..5a6f8d9 100644
--- a/test/rop/core_test.clj
+++ b/test/rop/core_test.clj
@@ -2,6 +2,8 @@
   (:require
     [clojure.string :refer [blank? lower-case]]
     [clojure.test :refer [deftest is testing]]
+    [cats.core :as m]
+    [struct.core :as st]
     [rop.core :as rop]))
 
 
@@ -83,3 +85,28 @@
                     validate-email
                     (rop/switch #(assoc % :new-user {:email (:email %), :id 1}))
                     (rop/dead send-email!))))))
+
+
+(deftest validate-request-test
+  (testing "should assoc a validated input"
+    (is (= {:request {:params {:id 1}}}
+           (m/extract (rop/=validate-request= st/validate
+                                              {:id [st/number-str]}
+                                              {}
+                                              :params
+                                              {:request {:params {:id "1"}}})))))
+
+  (testing "should assoc errors"
+    (is (= {:status 400, :body {:errors {:id "must be a number"}}}
+           (m/extract (rop/=validate-request= st/validate
+                                              {:id [st/number-str]}
+                                              {}
+                                              :params
+                                              {:request {:params {:id ""}}}))))))
+
+
+(deftest merge-params-test
+  (is (= {:request {:params {:id 1, :foo :bar}, :body-params {:foo :bar}}}
+         (m/extract (rop/=merge-params= :body-params
+                                        :params
+                                        {:request {:params {:id 1}, :body-params {:foo :bar}}})))))