Tests failing with Mockgoose cause MongoError: topology was destroyed

I'm running a series of tests with Mockgoose/Mongoose (using Mocha/Chai as the test suite).

If one of my tests happens to fail (ie. due to a failed .should.be.deep.equal()), all of the subsequent tests fail with the message MongoError: topology was destroyed

Here's some relevant snippets:

mockgoose(mongoose);

before(function(done) {
    mongoose.connect('mongodb://fake.test/TestingDB', function(err) {
        done(err);
    }); 
});

afterEach(function(done) {
    mockgoose.reset();
    done();
});

// Test Cases
describe('Testing the functions that deal with users and locations:', function() {
    // Test Setup
    var req

    beforeEach(function(done) {
        req = {};
        mockgoose.reset();
        done();
    });

    beforeEach(function(done) {
        sensors.create(testData.deviceData, function(err, model) {
            if (err) {console.log(err)};
            done();
        });
    });
    //tests start here

And here's an example of the errors I get:

1) Testing functions that use the Furnace collections Testing furnaceOn function Should produce some output:
   Uncaught TypeError: Cannot read property 'should' of undefined
    at C:\Users\Zachary Jacobi\Development\webapp\tests\unit\dbFunctionMockTests.js:417:11
    at Query.<anonymous> (C:\Users\Zachary Jacobi\Development\webapp\lib\dbFunctions.js:499:3)
    at C:\Users\Zachary Jacobi\Development\webapp\node_modules\mongoose\node_modules\kareem\index.js:177:19
    at C:\Users\Zachary Jacobi\Development\webapp\node_modules\mongoose\node_modules\kareem\index.js:109:16

2) Testing functions that use the Furnace collections "before each" hook for "Should produce the same results as the mock up from testData":
   MongoError: topology was destroyed
    at Server.insert (C:\Users\Zachary Jacobi\Development\webapp\node_modules\mongoose\node_modules\mongodb\node_modules\mongodb-core\lib\topologies\server.js:951:49)
    at Server.insert (C:\Users\Zachary Jacobi\Development\webapp\node_modules\mongoose\node_modules\mongodb\lib\server.js:324:17)
    at executeBatch (C:\Users\Zachary Jacobi\Development\webapp\node_modules\mongoose\node_modules\mongodb\lib\bulk\unordered.js:436:23)
    at executeBatches (C:\Users\Zachary Jacobi\Development\webapp\node_modules\mongoose\node_modules\mongodb\lib\bulk\unordered.js:457:5)
    at UnorderedBulkOperation.execute (C:\Users\Zachary Jacobi\Development\webapp\node_modules\mongoose\node_modules\mongodb\lib\bulk\unordered.js:515:44)
    at bulkWrite (C:\Users\Zachary Jacobi\Development\webapp\node_modules\mongoose\node_modules\mongodb\lib\collection.js:582:8)
    at Collection.insertMany (C:\Users\Zachary Jacobi\Development\webapp\node_modules\mongoose\node_modules\mongodb\lib\collection.js:477:44)
    at Collection.insert (C:\Users\Zachary Jacobi\Development\webapp\node_modules\mongoose\node_modules\mongodb\lib\collection.js:753:15)
    at NativeCollection.(anonymous function) [as insert] (C:\Users\Zachary Jacobi\Development\webapp\node_modules\mongoose\lib\drivers\node-mongodb-native\collection.js:136:28)
    at model.Model.$__handleSave (C:\Users\Zachary Jacobi\Development\webapp\node_modules\mongoose\lib\model.js:130:21)
    at model.Model.$__save (C:\Users\Zachary Jacobi\Development\webapp\node_modules\mongoose\lib\model.js:189:9)
    at model.Model.save (C:\Users\Zachary Jacobi\Development\webapp\node_modules\mongoose\lib\model.js:282:17)
    at model._done (C:\Users\Zachary Jacobi\Development\webapp\node_modules\mongoose\node_modules\hooks-fixed\hooks.js:101:24)
    at _next (C:\Users\Zachary Jacobi\Development\webapp\node_modules\mongoose\node_modules\hooks-fixed\hooks.js:64:28)
    at fnWrapper (C:\Users\Zachary Jacobi\Development\webapp\node_modules\mongoose\node_modules\hooks-fixed\hooks.js:186:18)
    at model.Object.defineProperty.value.fn (C:\Users\Zachary Jacobi\Development\webapp\node_modules\mongoose\lib\schema.js:250:9)
    at _next (C:\Users\Zachary Jacobi\Development\webapp\node_modules\mongoose\node_modules\hooks-fixed\hooks.js:62:30)
    at fnWrapper (C:\Users\Zachary Jacobi\Development\webapp\node_modules\mongoose\node_modules\hooks-fixed\hooks.js:186:18)
    at C:\Users\Zachary Jacobi\Development\webapp\node_modules\mongoose\lib\schema.js:233:13
    at complete (C:\Users\Zachary Jacobi\Development\webapp\node_modules\mongoose\lib\document.js:1131:5)
    at C:\Users\Zachary Jacobi\Development\webapp\node_modules\mongoose\lib\document.js:1157:20
    at Mixed.SchemaType.doValidate (C:\Users\Zachary Jacobi\Development\webapp\node_modules\mongoose\lib\schematype.js:654:22)
    at C:\Users\Zachary Jacobi\Development\webapp\node_modules\mongoose\lib\document.js:1153:9

Does anyone know what is causing this and what I can do to fix it? It's making it difficult to determine how many tests are actually failing when one failed test causes all subsequent ones to fail.