How to use VSCode and REPL to write and test a package?

Tooling VS Code
,
45

Neither instantiate nor resolve changed anything in any of the environments.

Proof 
(ASME_Materials) pkg> activate test
  Activating project at `C:\Users\nboyer.AIP\.julia\dev\ASME_Materials\test`

(test) pkg> status
      Status `C:\Users\nboyer.AIP\.julia\dev\ASME_Materials\test\Project.toml`
  [336ed68f] CSV v0.10.4
  [a93c6f00] DataFrames v1.3.3
  [c91e804a] Gadfly v1.3.4
  [23fbe1c1] Latexify v0.15.14
  [1986cc42] Unitful v1.11.0
  [8dfed614] Test

(test) pkg> instantiate

(test) pkg> resolve
  No Changes to `C:\Users\nboyer.AIP\.julia\dev\ASME_Materials\test\Project.toml`
  No Changes to `C:\Users\nboyer.AIP\.julia\dev\ASME_Materials\test\Manifest.toml`

(test) pkg> status
      Status `C:\Users\nboyer.AIP\.julia\dev\ASME_Materials\test\Project.toml`
  [c91e804a] Gadfly v1.3.4
  [23fbe1c1] Latexify v0.15.14
  [1986cc42] Unitful v1.11.0
  [8dfed614] Test

(test) pkg> activate .
  Activating project at `C:\Users\nboyer.AIP\.julia\dev\ASME_Materials`

(ASME_Materials) pkg> instantiate

(ASME_Materials) pkg> resolve
  No Changes to `C:\Users\nboyer.AIP\.julia\dev\ASME_Materials\Project.toml`
  No Changes to `C:\Users\nboyer.AIP\.julia\dev\ASME_Materials\Manifest.toml`

(ASME_Materials) pkg> instantiate

(ASME_Materials) pkg> status
     Project ASME_Materials v0.1.0
      Status `C:\Users\nboyer.AIP\.julia\dev\ASME_Materials\Project.toml`
  [336ed68f] CSV v0.10.4
  [a93c6f00] DataFrames v1.3.3
  [23fbe1c1] Latexify v0.15.14
  [1986cc42] Unitful v1.11.0

julia> using TestEnv; TestEnv.activate()
"C:\\Users\\nboyer.AIP\\AppData\\Local\\Temp\\jl_DrjBp3\\Project.toml"

(jl_DrjBp3) pkg> resolve
  No Changes to `C:\Users\nboyer.AIP\AppData\Local\Temp\jl_DrjBp3\Project.toml`
  No Changes to `C:\Users\nboyer.AIP\AppData\Local\Temp\jl_DrjBp3\Manifest.toml`

(jl_DrjBp3) pkg> instantiate

(jl_DrjBp3) pkg> status
      Status `C:\Users\nboyer.AIP\AppData\Local\Temp\jl_DrjBp3\Project.toml`
  [e596c8da] ASME_Materials v0.1.0 `C:\Users\nboyer.AIP\.julia\dev\ASME_Materials`
  [336ed68f] CSV v0.10.4
  [a93c6f00] DataFrames v1.3.3
  [c91e804a] Gadfly v1.3.4
  [23fbe1c1] Latexify v0.15.14
  [1986cc42] Unitful v1.11.0
  [8dfed614] Test `@stdlib/Test`