test: add cmdtest package (#15251)

## Description

This PR introduces the `cmdtest` package, offering a lightweight wrapper around cobra commands to simplify testing CLI utilities.

I backfilled tests for the `version` command, which was an example of a very simple test setup; and for the `export` command, which was more involved due to the server and client context requirements.

I did notice that there are some existing tests for some utilities, but the `cmdtest` package follows a simple pattern that has been easy to use successfully in [the relayer](https://github.com/cosmos/relayer/blob/main/internal/relayertest/system.go) and in other projects outside the Cosmos ecosystem.

While filling in these tests, I started removing uses of `cmd.Print`, as that is the root cause of issues like #8498, #7964, #15167, and possibly others. Internal to cobra, the print family of methods write to `cmd.OutOrStderr()` -- meaning that if the authors call `cmd.SetOutput()` before executing the command, the output will be written to stdout as expected; otherwise it will go to stderr. I don't understand why that would be the default behavior, but it is probably too late to change from cobra's side.

Instead of `cmd.Print`, we prefer to `fmt.Fprint(cmd.OutOrStdout())` or `fmt.Fprint(cmd.ErrOrStderr())` as appropriate, giving an unambiguous destination for output. And the new tests collect those outputs in plain `bytes.Buffer` values so that we can assert their content appropriately.

In the longer term, I would like to deprecate and eventually remove the `testutil` package's `ApplyMockIO` method and its `BufferWriter` and `BufferReader` types, as they are unnecessary indirection when a simpler solution exists. But that can wait until `cmdtest` has propagated through the codebase more.

---

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This commit is contained in:

Mark Rushakoff

2023-03-06 19:40:24 +00:00

committed by

GitHub

parent f151bf627a

commit e7097b1468

6 changed files with 602 additions and 13 deletions

									
										server/types/app.go
									
		+10
		-1
	
												View File
												
				@@ -78,5 +78,14 @@ type (

					// AppExporter is a function that dumps all app state to

					// JSON-serializable structure and returns the current validator set.

					AppExporter func(log.Logger, dbm.DB, io.Writer, int64, bool, []string, AppOptions, []string) (ExportedApp, error)

					AppExporter func(

						logger log.Logger,

						db dbm.DB,

						traceWriter io.Writer,

						height int64,

						forZeroHeight bool,

						jailAllowedAddrs []string,

						opts AppOptions,

						modulesToExport []string,

					) (ExportedApp, error)

				)