Add the required number of tests [HELP WANTED]

[fulldecent]

According to CocoaPods, our testing is deficient.

Evidence: https://travis-ci.org/fulldecent/FDWaveformView/builds/222183787#L466

Work plan

• [ ] Identify exactly what causes that metric to fail
• [ ] Update https://github.com/fulldecent/swift3-module-template and https://github.com/fulldecent/swift3-module-template/blob/master/PROJECT_NAME/Tests/CheckCocoaPodsQualityIndexes.rb to output said explanation directly into the Travis console output
• [ ] Fix the thing