Add more test machine commands for inspecting its state

[99-not-out]

Added two new Test Machine commands.

:do! - like do but the function provided is passed the journal atom, not the contents of the journal atom.

:inspect - the function provided is passed the whole test machine state (a debugging hook)

[codecov-io]

Codecov Report

Merging #141 into master will increase coverage by 0.03%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #141      +/-   ##
==========================================
+ Coverage      81%   81.04%   +0.03%     
==========================================
  Files          39       39              
  Lines        2317     2321       +4     
  Branches      147      147              
==========================================
+ Hits         1877     1881       +4     
  Misses        293      293              
  Partials      147      147

Impacted Files	Coverage Δ
src/jackdaw/test/commands/base.clj	100% <100%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 1722d6d...eca15fb. Read the comment docs.

[cddr]

Seems reasonable. Can you add the new commands to the docs plz?

https://github.com/FundingCircle/jackdaw/blob/master/doc/test-machine.md#test-commands

[creese]

Seems like one is a superset of the other? Should we just change how :do behaves?

[99-not-out]

Well, the difference between do and do! is that do will give you a static snapshot of the journal state at the time do ran. Where as do! returns the atom, which is therefore still being updated in the background. So do! lets you inject some custom journal update monitoring or whatever code.

do! and inspect are really debugging commands as a result.