Set up SynthDiag tests to respect newARGS for passing in test flags f…

…rom within a julia session

test/runtests.jl

@@ -10,6 +10,8 @@ using DelimitedFiles: readdlm
 using Interpolations: linear_interpolation
 
 function parse_commandline()
+    # Define newARGS = ["--yourflag"] to run only tests on your flags when including runtests.jl
+    localARGS = @isdefined(newARGS) ? newARGS : ARGS  # Thanks https://stackoverflow.com/a/44978474/6605826
     s = ArgParse.ArgParseSettings(; description="Run tests. Default is all tests.")
 
     ArgParse.add_arg_table!(s,
@@ -23,7 +25,7 @@ function parse_commandline()
         Dict(:help => "Test only gas injection",
             :action => :store_true),
     )
-    args = ArgParse.parse_args(s)
+    args = ArgParse.parse_args(localARGS, s)
     if !any(values(args)) # If no flags are set, run all tests
         for k ∈ keys(args)
             args[k] = true