test: use ParallelTestRunner.jl (#277)

Use ParallelTestRunner.jl for subpackage tests. Tests are refactored
into their own files to leverage parallelization.

Author: icweaver

.github/workflows/Tests.yml

@@ -83,6 +83,8 @@ jobs:
             ${{ runner.os }}-
       - uses: julia-actions/julia-buildpkg@v1
       - uses: julia-actions/julia-runtest@v1
+        with:
+          test_args: "--verbose"
         env:
           GROUP: "GeneralAstrodynamics"
       - uses: julia-actions/julia-processcoverage@v1

README.md

@@ -96,13 +96,33 @@ or navigate to top-level of `<subpackage>` and run tests as usual:
 (GeneralAstrodynamics/lib/AstrodynamicalCalculations) pkg> test
 ```
 
-### Explicit imports
+List available tests for a given <subpackage>:
 
-See the documentation for [`ExplicitImports.jl`]() for standard usage. For non-package files at path `<fpath>` relative to the top-level of `<subpackage>`, run the following:
+```julia-repl
+> julia --proj
+
+julia> using Pkg
+
+julia> Pkg.test("<subpackage>"; test_args = `--list`)
+```
+
+Run specific tests for a given <subpackage>:
 
 ```julia-repl
 > julia --proj
 
+julia> using Pkg
+
+julia> Pkg.test("<subpackage>"; test_args = `--verbose <filename>`)
+```
+
+for a given filename listed in the previous usage example. Partial matches for the start of the filename are also accepted.
+
+### Explicit imports
+
+See the documentation for [`ExplicitImports.jl`]() for standard usage. For non-package files at path `<fpath>` relative to the top-level of `<subpackage>`, run the following:
+
+```julia-repl
 julia> using ExplicitImports, <subpackage>
 
 julia> include(<fpath>)