diff --git a/lib/db/mysql/index.js b/lib/db/mysql/index.js
index 07915e2b6..fcabeae28 100644
--- a/lib/db/mysql/index.js
+++ b/lib/db/mysql/index.js
@@ -68,7 +68,6 @@ function checkDbPatchLevel(patcher) {
 
   patcher.readDbPatchLevel(function(err) {
     if (err) {
-      logger.error('checkDbPatchLevel', err);
       return d.reject(err);
     }
     // We are only guaranteed to run correctly if we're at the current
@@ -77,7 +76,6 @@ function checkDbPatchLevel(patcher) {
     if (patcher.currentPatchLevel !== patch.level) {
       if (patcher.currentPatchLevel !== patch.level + 1) {
         err = 'unexpected db patch level: ' + patcher.currentPatchLevel;
-        logger.error('checkDbPatchLevel', err);
         return d.reject(new Error(err));
       }
     }
@@ -105,6 +103,9 @@ MysqlStore.connect = function mysqlConnect(options) {
     return checkDbPatchLevel(patcher);
   }).then(function() {
     return P.promisify(patcher.end, patcher)();
+  }, function(error) {
+    logger.error('checkDbPatchLevel', error);
+    patcher.end(process.exit.bind(process, 1));
   }).then(function() {
     return new MysqlStore(options);
   });
diff --git a/package.json b/package.json
index dd247d2c8..d4bc47e82 100644
--- a/package.json
+++ b/package.json
@@ -54,7 +54,9 @@
     "load-grunt-tasks": "^3.1.0",
     "mocha-text-cov": "^0.1.0",
     "nock": "^1.2.1",
+    "proxyquire": "^1.6.0",
     "read": "^1.0.5",
+    "sinon": "^1.15.4",
     "time-grunt": "^1.1.0"
   }
 }
diff --git a/test/db.js b/test/db/index.js
similarity index 99%
rename from test/db.js
rename to test/db/index.js
index 958ffe3eb..ca854d728 100644
--- a/test/db.js
+++ b/test/db/index.js
@@ -8,8 +8,8 @@ const assert = require('insist');
 const buf = require('buf').hex;
 const hex = require('buf').to.hex;
 
-const db = require('../lib/db');
-const config = require('../lib/config');
+const db = require('../../lib/db');
+const config = require('../../lib/config');
 
 /*global describe,it,before*/
 
diff --git a/test/db/mysql.js b/test/db/mysql.js
new file mode 100644
index 000000000..da10fcd98
--- /dev/null
+++ b/test/db/mysql.js
@@ -0,0 +1,200 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const assert = require('insist');
+const sinon = require('sinon');
+const mocks = require('../lib/mocks');
+
+const modulePath = '../../lib/db/mysql';
+
+var instances = {};
+var dependencies = mocks.require([
+  { path: 'buf' },
+  { path: 'mysql' },
+  { path: 'mysql-patcher', ctor: function() { return instances.patcher; } },
+  { path: '../../config' },
+  { path: '../../encrypt' },
+  { path: '../../logging', ctor: function() { return instances.logger; } },
+  { path: '../../scope' },
+  { path: '../../unique', ctor: function() { return instances.scope; } },
+  { path: './patch' }
+], modulePath, __dirname);
+
+function nop() {
+}
+
+function callback(cb) {
+  cb();
+}
+
+process.setMaxListeners(0);
+
+describe('db/mysql:', function() {
+  var sandbox, mysql;
+
+  beforeEach(function() {
+    sandbox = sinon.sandbox.create();
+
+    sandbox.stub(dependencies['../../config'], 'get', function() {
+      return 'mock config.get result';
+    });
+    instances.logger = {
+      info: nop,
+      debug: nop,
+      warn: nop,
+      error: nop,
+      verbose: nop
+    };
+    Object.keys(instances.logger).forEach(function(methodName) {
+      sandbox.spy(instances.logger, methodName);
+    });
+
+    mocks.register(dependencies, modulePath, __dirname);
+
+    mysql = require(modulePath);
+  });
+
+  afterEach(function() {
+    sandbox.restore();
+    mocks.deregister();
+  });
+
+  it('exports a connect function', function() {
+    assert.equal(typeof mysql.connect, 'function');
+  });
+
+  describe('connect:', function() {
+    beforeEach(function() {
+      instances.patcher = {
+        connect: nop,
+        patch: nop,
+        readDbPatchLevel: nop,
+        end: nop,
+        currentPatchLevel: dependencies['./patch'].level
+      };
+      sandbox.stub(instances.patcher, 'connect', callback);
+      sandbox.stub(instances.patcher, 'patch', nop);
+      sandbox.stub(instances.patcher, 'end', callback);
+      sandbox.stub(process, 'exit', nop);
+    });
+
+    describe('readDbPatchLevel succeeds:', function() {
+      beforeEach(function() {
+        sandbox.stub(instances.patcher, 'readDbPatchLevel', function(callback) {
+          callback();
+        });
+      });
+
+      describe('db patch level is okay:', function() {
+        var result;
+
+        beforeEach(function() {
+          return mysql.connect({}).then(function(r) {
+            result = r;
+          });
+        });
+
+        it('called patcher.connect', function() {
+          assert.equal(instances.patcher.connect.callCount, 1);
+          var args = instances.patcher.connect.getCall(0).args;
+          assert.equal(args.length, 1);
+          assert.equal(typeof args[0], 'function');
+          assert.equal(args[0].length, 2);
+        });
+
+        it('did not call patcher.patch', function() {
+          assert.equal(instances.patcher.patch.callCount, 0);
+        });
+
+        it('called patcher.readDbPatchLevel', function() {
+          assert.equal(instances.patcher.readDbPatchLevel.callCount, 1);
+          var args = instances.patcher.readDbPatchLevel.getCall(0).args;
+          assert.equal(args.length, 1);
+          assert.equal(typeof args[0], 'function');
+          assert.equal(args[0].length, 1);
+        });
+
+        it('called patcher.end', function() {
+          assert.equal(instances.patcher.end.callCount, 1);
+          var args = instances.patcher.end.getCall(0).args;
+          assert.equal(args.length, 1);
+          assert.equal(typeof args[0], 'function');
+          assert.equal(args[0].length, 2);
+        });
+
+        it('did not call logger.error', function() {
+          assert.equal(instances.logger.error.callCount, 0);
+        });
+
+        it('did not call process.exit', function() {
+          assert.equal(process.exit.callCount, 0);
+        });
+
+        it('returned an object', function () {
+          assert.equal(typeof result, 'object');
+          assert.notEqual(result, null);
+        });
+      });
+
+      describe('db patch level is bad:', function() {
+        beforeEach(function() {
+          instances.patcher.currentPatchLevel += 2;
+          return mysql.connect({});
+        });
+
+        afterEach(function() {
+          instances.patcher.currentPatchLevel -= 2;
+        });
+
+        it('called patcher.end', function() {
+          assert.equal(instances.patcher.end.callCount, 1);
+        });
+
+        it('called logger.error', function() {
+          assert.equal(instances.logger.error.callCount, 1);
+          var args = instances.logger.error.getCall(0).args;
+          assert.equal(args.length, 2);
+          assert.equal(args[0], 'checkDbPatchLevel');
+          assert(args[1] instanceof Error);
+          assert.equal(args[1].message, 'unexpected db patch level: ' + (dependencies['./patch'].level + 2));
+        });
+
+        it('called process.exit', function() {
+          assert.equal(process.exit.callCount, 1);
+          var args = process.exit.getCall(0).args;
+          assert.equal(args.length, 1);
+          assert.equal(args[0], 1);
+        });
+      });
+    });
+
+    describe('readDbPatchLevel fails:', function() {
+      beforeEach(function() {
+        sandbox.stub(instances.patcher, 'readDbPatchLevel', function(callback) {
+          callback('foo');
+        });
+        return mysql.connect({});
+      });
+
+      it('called patcher.end', function() {
+        assert.equal(instances.patcher.end.callCount, 1);
+      });
+
+      it('called logger.error', function() {
+        assert.equal(instances.logger.error.callCount, 1);
+        var args = instances.logger.error.getCall(0).args;
+        assert.equal(args[0], 'checkDbPatchLevel');
+        assert.equal(args[1], 'foo');
+      });
+
+      it('called process.exit', function() {
+        assert.equal(process.exit.callCount, 1);
+        var args = process.exit.getCall(0).args;
+        assert.equal(args.length, 1);
+        assert.equal(args[0], 1);
+      });
+    });
+  });
+});
+
diff --git a/test/lib/mocks.js b/test/lib/mocks.js
new file mode 100644
index 000000000..fbc42c497
--- /dev/null
+++ b/test/lib/mocks.js
@@ -0,0 +1,111 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const path = require('path');
+const proxyquire = require('proxyquire');
+const m = require('module');
+
+var moduleCache;
+
+module.exports = {
+  require: requireDependencies,
+  register: registerDependencies,
+  deregister: deregisterDependencies
+};
+
+// `mocks.require`
+//
+// Require dependencies using the same path that is specifed in the module
+// under test.
+//
+// Returns an object containing dependencies keyed by their path.
+//
+// Expects three arguments; `dependencies`, `modulePath` and `basePath`.
+//
+// dependencies: Array of { path, ctor } items.
+//               path: The dependency path, as specified in the module
+//                     under test.
+//               ctor: Optional. If the dependency is a constructor for
+//                     an instance that you wish to mock, set this to a
+//                     function that returns your mock instance.
+// modulePath:   The relative path to the module under test.
+// basePath:     The base path, i.e. __dirname for the test itself.
+function requireDependencies(dependencies, modulePath, basePath) {
+  var result = {};
+
+  dependencies.forEach(function (dependency) {
+    result[dependency.path] = requireDependency(dependency, modulePath, basePath);
+  });
+
+  return result;
+}
+
+function requireDependency(dependency, modulePath, basePath) {
+  if (typeof dependency.ctor === 'function') {
+    return dependency.ctor;
+  }
+
+  var localPath = dependency.path;
+
+  if (localPath[0] === '.') {
+    localPath = path.relative(
+      basePath,
+      path.resolve(basePath, modulePath, localPath)
+    );
+  }
+
+  return require(localPath);
+}
+
+// `mocks.register`
+//
+// Register mock dependencies, fixing paths as we go so that it works
+// with the blanket coverage tool (which rewrites require paths in the
+// instrumented code). You should call this function inside beforeEach.
+//
+// Expects three arguments; `dependencies`, `modulePath` and `basePath`.
+//
+// dependencies: An object, where keys are dependency paths and values
+//               are mock objects. This argument is typically the return
+//               value from `mocks.require`, modified by sinon for your
+//               tests.
+// modulePath:   The relative path to the module under test.
+// basePath:     The base path, i.e. __dirname for the test itself.
+function registerDependencies(dependencies, modulePath, basePath) {
+  var instrumentedDependencies = {};
+
+  clearModuleCache();
+
+  Object.keys(dependencies).forEach(function(dependencyPath) {
+    var instrumentedPath = getInstrumentedPath(dependencyPath, modulePath, basePath);
+    instrumentedDependencies[instrumentedPath] = dependencies[dependencyPath];
+  });
+
+  proxyquire(modulePath, instrumentedDependencies);
+}
+
+function clearModuleCache() {
+  moduleCache = m._cache;
+  m._cache = {};
+}
+
+function getInstrumentedPath(dependencyPath, modulePath, basePath) {
+  if (dependencyPath[0] !== '.') {
+    return dependencyPath;
+  }
+
+  return path.resolve(basePath, modulePath) + '/' + dependencyPath;
+}
+
+// `mocks.deregister`
+//
+// Deregister mock dependencies. You should call this function
+// inside afterEach.
+function deregisterDependencies() {
+  if (moduleCache) {
+    m._cache = moduleCache;
+    moduleCache = null;
+  }
+}
+