security/reliability: Add basic fuzz-testing harness

[silvergasp]

No description provided.

[silvergasp]

If you are not familiar with fuzz testing using golang here is a brief intro on how to get started with this fuzz-testing harness. All you need to do is run;

$ go test -fuzz=FuzzSVG  oss.terrastruct.com/d2/fuzz
fuzz: elapsed: 0s, gathering baseline coverage: 0/51 completed
fuzz: elapsed: 1s, gathering baseline coverage: 51/51 completed, now fuzzing with 8 workers
fuzz: elapsed: 3s, execs: 193 (64/sec), new interesting: 1 (total: 52)
fuzz: elapsed: 6s, execs: 205 (4/sec), new interesting: 2 (total: 53)
fuzz: elapsed: 9s, execs: 300 (32/sec), new interesting: 2 (total: 53)
fuzz: elapsed: 12s, execs: 318 (6/sec), new interesting: 2 (total: 53)
fuzz: elapsed: 15s, execs: 678 (120/sec), new interesting: 3 (total: 54)
fuzz: elapsed: 18s, execs: 932 (85/sec), new interesting: 5 (total: 56)
fuzz: elapsed: 21s, execs: 987 (18/sec), new interesting: 5 (total: 56)
fuzz: elapsed: 24s, execs: 1195 (69/sec), new interesting: 7 (total: 58)
^Cfuzz: elapsed: 27s, execs: 1204 (3/sec), new interesting: 8 (total: 59)
fuzz: elapsed: 27s, execs: 1204 (0/sec), new interesting: 8 (total: 59)
PASS
ok      oss.terrastruct.com/d2/fuzz     27.306s

The fuzz harness will run indefinetely or until;

• It crashes the d2 library
• You manually exit (ctrl-C)
• You specify a timeout on the command line.

[alixander]

Discussion here: #1664