A TDD exercise based on parsing and decoding aviation weather METAR data in Java. A typical METAR looks like this:
CYOW 081900Z 33007KT 15SM -RA SCT030TCU BKN100 BKN180 24/22 A2984 RMK TCU4AC2AC1 SLP107 DENSITY ALT 1600FT
This is read as:
- Station: Ottawa Macdonald/Cartier Airport, ICAO code 'CYOW'
- Reporting Time: the day of the month 08, time in 'Zulu' or UTC 19:00
- Wind Velocity: 330 degrees at 7 knots
- Visibility: 15 statute miles
- Conditions: -RA, light rain
- Clouds:
- Scattered, 3000 feet AGL (above ground level), towering cumulus (TCU)
- Broken, 10000 feet AGL
- Broken, 18000 feet AGL
- Temperature & Dewpoint: 24C and 22C, respectively
- Altimeter Setting: 29.84 inches of mercury
- Remarks: (not implementing them in this exercise)
The definitions and specifications used for the code are found in MANOBS Manual of Surface Weather Observations: aviation routine weather report from Environment Canada.
The master branch contains the final version of the Java code used in the TDD exercise. Interim steps are contained in the various branches.
The overall goals of the exercise were:
- using a truly test-driven approach to building code
- focusing on what's really important first, in this case parsing & decoding the raw METAR rather than building the service to retrieve it
- showing that you can ship a usable product without needing 100% of the functionality completed
- not requiring a mocking library in order to create test doubles (one can be used, but isn't necessary)
- using concrete examples of data to drive design and development