fix(test): remove specs that cannot fail, and fix one whose name lied

[tas50]

Seven tests removed, one rewritten. Every removal was verified by mutation — break the thing the test claims to guard, confirm the suite still catches it.

353 runs / 1155 assertions, down from 360 / 1179.

Method

For each candidate, mutate lib/ and record which spec files fail:

Mutation	Before	After
add a global url= setter to Client	regression	regression
reparent NotFound outside the hierarchy	5 files	5 files
container_create drops platform from the query	3 files	3 files
drop platform from the signature	3 files	3 files
npipe URLs route to Tcp	regression + transport	transport
add a method to ::Docker	regression + version	regression
break the Windows pipe constant	regression	regression
default_url ignores Windows entirely	nothing	regression
break the unix socket constant	nothing	regression

Two mutations that nothing caught before are caught now.

Cannot fail at all

session_spec — "constructs without going through Net::HTTP.new's proxy handling"

_(session).must_be_kind_of Net::HTTP   # true by `class Session < Net::HTTP`
_(session.proxy?).must_equal false

proxy? is false in every configuration — including @proxy_from_env forced true with http_proxy set — because the address is localhost. Verified directly. The regression it names is caught by the two tests above it, which could not construct a session at all.

fake_spec — "is a real socket, so it satisfies what Net::BufferedIO asks of one" asserts a UNIXSocket responds to read_nonblock, write, to_io. That is Ruby's stdlib. The three tests above it already drive a real HTTP exchange through the fake.

regression — "puts everything under Docker::API" — Client.name restated from its own declaration.

regression — "resolves registry credentials per call" — respond_to? :resolve on a module_function declared three lines away in the source. auth_spec exercises resolve behaviourally nine times.

Strictly duplicated

• version_spec "defines no methods on ::Docker" — same mutation, same catch, as the regression spec's "adds nothing to ::Docker".
• regression "builds a named-pipe transport from a npipe URL" — transport_spec covers npipe routing, which is where transport routing belongs.
• regression "declares every query parameter the specification defines" — reflection over the signature. Dropping platform from the query hash fails the wire assertion directly above it while this one passes; dropping it from the signature fails both. A strict subset.

Superseded

regression — "loads no HTTP gem at all" greps $LOADED_FEATURES for four named gems — which only populates if the gem is actually installed:

excon            allowlist catches: true  | LOADED_FEATURES grep could catch: false
some-random-gem  allowlist catches: true  | LOADED_FEATURES grep could catch: false

zero_dependency_spec holds every require in lib/ to an allowlist of default gems. It catches all four plus the ones nobody thought to name.

Rewritten, not removed

regression — "defaults to the named pipe on Windows" was:

_(Docker::API::Config::DEFAULT_WINDOWS_PIPE).must_include "pipe/docker_engine"

A constant containing a substring of itself. The name promised routing; the body checked spelling. Deleting the Windows branch from default_url was caught by nothing in the suite.

It now stubs windows? and asserts default_url both ways — against literals rather than the constants, since comparing default_url to DEFAULT_WINDOWS_PIPE only proves the two agree with each other. Those literals are an external contract: the pipe Docker Desktop actually publishes.

What I checked and kept

Three I expected to cut turned out to earn their place, and the mutations say so:

• "offers no way to change a daemon out from under a live client" — hand-lists five method names, which read as weak. Adding Client.url= is caught by this test and nothing else.
• "defaults to the named pipe on Windows" (the constant check) did catch a broken constant — it just missed the routing. Hence rewrite rather than delete.
• errors_spec "keeps every error under the one root" restates the class hierarchy, but it is the test that names the gem's central promise and gives the clearest failure message.

Verification

bundle exec rake — 353 runs, 0 failures. steep check clean. Chefstyle clean. Full mutation table above re-run against the trimmed suite.