Step 4: make the first test pass

This is not proper Kent Beckian triangulation, because 
I threw the if() statement in there before it was properly
required by the test. In practice I'll probably comment out
the branch with and without the tests to ensure it's being
demanded properly, which is hard to capture in a git log

src/verify/index.js

@@ -1,9 +1,17 @@
+import CallLog from '../value/call-log'
+
+import ensureDemonstration from './ensure-demonstration'
+import didCallOccur from './did-call-occur'
+import notifySatisfiedMatchers from './notify-satisfied-matchers'
+import warnIfAlsoStubbed from './warn-if-also-stubbed'
+
 export default function verify (__userInvokesDemonstrationHere__, config) {
-  // 1. double, call = CallLog.instance.pop
-  // 2. ensureDemonstration(call)
-  // 3. if call-occurred (double, call, config)
-  //   a. notify-satisfied-matchers(double, call, config)
-  //   b. warn-if-also-stubbed (double, call)
+  const {double, call} = CallLog.instance.pop()
+  ensureDemonstration(call)
+  if (didCallOccur(double, call, config)) {
+    notifySatisfiedMatchers(double, call, config)
+    warnIfAlsoStubbed(double, call, config)
+  }
   // 4. else
   //   a. fail-verification (double, call, config)
 }