Initialize a test counter, a matrix used to tally tests, their stack depth and the execution order as the trace associated with key is hit. Each test trace is an environment, which allows assignment into a pre-allocated tests matrix with minimall reallocation.

new_test_counter(key)

## Arguments

key

generated with key()

## Details

The tests matrix has columns tests, depth and i, corresponding to the test index (the index of the associated test in .counters\$tests), the stack depth when the trace is evaluated and the number of traces that have been hit so far during test evaluation.