diff --git a/SwiftDraft/ReliantFramework/ReliantFramework/ReliantContext.swift b/SwiftDraft/ReliantFramework/ReliantFramework/ReliantContext.swift
index cb55481..3f5ac00 100644
--- a/SwiftDraft/ReliantFramework/ReliantFramework/ReliantContext.swift
+++ b/SwiftDraft/ReliantFramework/ReliantFramework/ReliantContext.swift
@@ -14,7 +14,6 @@ public protocol ReliantContext {
     static func createContext() -> ContextType
 }
 
-
 public protocol ReliantContextHolder {
     typealias ContextType : ReliantContext
     var context:ContextType { get }
diff --git a/SwiftDraft/ReliantFramework/ReliantFramework/RelyOn.swift b/SwiftDraft/ReliantFramework/ReliantFramework/RelyOn.swift
index 5659f57..85d65b4 100644
--- a/SwiftDraft/ReliantFramework/ReliantFramework/RelyOn.swift
+++ b/SwiftDraft/ReliantFramework/ReliantFramework/RelyOn.swift
@@ -8,17 +8,31 @@
 
 import Foundation
 
-class ContextCache {
-    static let sharedInstance:ContextCache = ContextCache()
-    var cache:Dictionary<String, Any> = Dictionary()
+struct ContextCache {
+    // If we're only going to use a static cache, we might as well use a struct?
+    static var standard = [String:Any]()
+    
+    static var substitutions = [String:Any.Type]()
 }
 
 public func relyOn<T:ReliantContext>(type:T.Type) -> T.ContextType {
-    if let result = ContextCache.sharedInstance.cache[String(type)] {
+    let typeKey = String(type)
+    if let result = ContextCache.standard[typeKey] {
         return result as! T.ContextType
     } else {
-        let result = type.createContext()
-        ContextCache.sharedInstance.cache[String(type)] = result
+        var result:T.ContextType
+        
+        if let substitutionType = ContextCache.substitutions[typeKey] as? T.Type {
+            result = substitutionType.createContext()
+        } else {
+            result = type.createContext()
+        }
+        
+        ContextCache.standard[String(type)] = result
         return result;
     }
+}
+
+public func relyOnSubstitute<T:ReliantContext>(type:T.Type)(_ otherType:T.Type) {
+    ContextCache.substitutions[String(type)] = otherType
 }
\ No newline at end of file
diff --git a/SwiftDraft/ReliantFramework/ReliantFrameworkTests/ReliantFrameworkTests.swift b/SwiftDraft/ReliantFramework/ReliantFrameworkTests/ReliantFrameworkTests.swift
index 8fb42b6..5509d80 100644
--- a/SwiftDraft/ReliantFramework/ReliantFrameworkTests/ReliantFrameworkTests.swift
+++ b/SwiftDraft/ReliantFramework/ReliantFrameworkTests/ReliantFrameworkTests.swift
@@ -54,17 +54,25 @@ struct ContextNeedingContext : ReliantContext {
         return ContextNeedingContext()
     }
 }
+class SubWaver : Waver {
+    func wave(reason: String) -> String {
+        return "Substitute waving"
+    }
+}
 
-
-
-
+class SubstituteContext : SimpleReferenceContext {
+    override init() {
+        super.init()
+        waver = SubWaver()
+    }
+}
 
 class ReliantFrameworkTests: XCTestCase {
     
     override func setUp() {
         super.setUp()
         ReliantFrameworkTestsHelper.sharedInsance.reset()
-        ContextCache.sharedInstance.cache = Dictionary()
+        ContextCache.standard.removeAll()
     }
     
     func testRelyOnReturnsSameInsanceEveryTimeForReferenceTypes() {
@@ -84,6 +92,17 @@ class ReliantFrameworkTests: XCTestCase {
         XCTAssertEqual(needed.needy.decorateGreeting(), "Oh! Hello Needy")
     }
     
-    
+    func testSubstitutions() {
+        relyOnSubstitute(SimpleReferenceContext)(SubstituteContext)
+        XCTAssertTrue(ContextCache.substitutions.contains({ (key, value) -> Bool in
+            return key == String(SimpleReferenceContext) && value == SubstituteContext.self
+        }))
         
+        let context = relyOn(SimpleReferenceContext)
+                
+        // Failing test.
+        // The createContext() function is static and thus final. Actual context type seems
+        // to be correct, but createContext() is called on original context class
+        XCTAssertTrue(context is SubstituteContext)
+    }
 }
diff --git a/SwiftDraft/ReliantFramework/ReliantFrameworkTests/SimpleReferenceContext.swift b/SwiftDraft/ReliantFramework/ReliantFrameworkTests/SimpleReferenceContext.swift
index 7bc1bc3..54ce590 100644
--- a/SwiftDraft/ReliantFramework/ReliantFrameworkTests/SimpleReferenceContext.swift
+++ b/SwiftDraft/ReliantFramework/ReliantFrameworkTests/SimpleReferenceContext.swift
@@ -12,8 +12,8 @@ import Reliant
 class SimpleReferenceContext : ReliantContext {
     private let bothWorlds = BothWorlds(prefix:"Hello")
     
-    let waver:Waver
-    let greeter:Greeter
+    var waver:Waver
+    var greeter:Greeter
     
     init() {
         ReliantFrameworkTestsHelper.sharedInsance.markInitCalled()