Initial work on null (object) double

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Michael Miller 2022-03-12 17:07:34 -07:00
parent 1e7e31ff97
commit ca827a3c52
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require "../../spec_helper"
Spectator.describe Spectator::NullDouble do
Spectator::NullDouble.define(EmptyDouble)
Spectator::NullDouble.define(FooBarDouble, "dbl-name", foo: 42, bar: "baz")
private macro expect_null_double(double, actual)
%actual_box = Box.box({{actual}})
%double_box = Box.box({{double}})
expect(%actual_box).to eq(%double_box), {{actual.stringify}} + " is not " + {{double.stringify}}
end
# The subject `dbl` must be carefully used in sub-contexts, otherwise it pollutes parent scopes.
# This changes the type of `dbl` to `Double`, which produces a union of methods and their return types.
context "plain double" do
subject(dbl) { FooBarDouble.new }
it "responds to defined messages" do
aggregate_failures do
expect(dbl.foo).to eq(42)
expect(dbl.bar).to eq("baz")
end
end
it "returns self on undefined messages" do
expect_null_double(dbl, dbl.baz)
end
it "has a non-union return type" do
aggregate_failures do
expect(dbl.foo).to compile_as(Int32)
expect(dbl.bar).to compile_as(String)
end
end
end
context "with common object methods" do
subject(dbl) do
EmptyDouble.new([
Spectator::ValueStub.new(:"!=", "!="),
Spectator::ValueStub.new(:"!~", "!~"),
Spectator::ValueStub.new(:"==", "=="),
Spectator::ValueStub.new(:"===", "==="),
Spectator::ValueStub.new(:"=~", "=~"),
Spectator::ValueStub.new(:class, "class"),
Spectator::ValueStub.new(:dup, "dup"),
Spectator::ValueStub.new(:hash, "hash"),
Spectator::ValueStub.new(:"in?", true),
Spectator::ValueStub.new(:inspect, "inspect"),
Spectator::ValueStub.new(:itself, "itself"),
Spectator::ValueStub.new(:"not_nil!", "not_nil!"),
Spectator::ValueStub.new(:pretty_inspect, "pretty_inspect"),
Spectator::ValueStub.new(:tap, "tap"),
Spectator::ValueStub.new(:to_json, "to_json"),
Spectator::ValueStub.new(:to_pretty_json, "to_pretty_json"),
Spectator::ValueStub.new(:to_s, "to_s"),
Spectator::ValueStub.new(:to_yaml, "to_yaml"),
Spectator::ValueStub.new(:try, "try"),
Spectator::ValueStub.new(:object_id, 42_u64),
Spectator::ValueStub.new(:"same?", true),
] of Spectator::Stub)
end
it "responds with defined messages" do
aggregate_failures do
expect(dbl.!=(42)).to eq("!=")
expect(dbl.!~(42)).to eq("!~")
expect(dbl.==(42)).to eq("==")
expect(dbl.===(42)).to eq("===")
expect(dbl.=~(42)).to eq("=~")
expect(dbl.class).to eq("class")
expect(dbl.dup).to eq("dup")
expect(dbl.hash(42)).to eq("hash")
expect(dbl.hash).to eq("hash")
expect(dbl.in?(42)).to eq(true)
expect(dbl.in?(1, 2, 3)).to eq(true)
expect(dbl.inspect).to eq("inspect")
expect(dbl.itself).to eq("itself")
expect(dbl.not_nil!).to eq("not_nil!")
expect(dbl.pretty_inspect).to eq("pretty_inspect")
expect(dbl.tap { nil }).to eq("tap")
expect(dbl.to_json).to eq("to_json")
expect(dbl.to_pretty_json).to eq("to_pretty_json")
expect(dbl.to_s).to eq("to_s")
expect(dbl.to_yaml).to eq("to_yaml")
expect(dbl.try { nil }).to eq("try")
expect(dbl.object_id).to eq(42_u64)
expect(dbl.same?(dbl)).to eq(true)
expect(dbl.same?(nil)).to eq(true)
end
end
it "has a non-union return type" do
expect(dbl.inspect).to compile_as(String)
end
end
context "without common object methods" do
subject(dbl) { EmptyDouble.new }
it "returns self with undefined messages" do
io = IO::Memory.new
pp = PrettyPrint.new(io)
aggregate_failures do
expect_null_double(dbl, dbl.!=(42))
expect_null_double(dbl, dbl.!~(42))
expect_null_double(dbl, dbl.==(42))
expect_null_double(dbl, dbl.===(42))
expect_null_double(dbl, dbl.=~(42))
expect_null_double(dbl, dbl.class)
expect_null_double(dbl, dbl.dup)
expect_null_double(dbl, dbl.hash(42))
expect_null_double(dbl, dbl.hash)
# expect(dbl.in?(42)).to be(dbl)
# expect(dbl.in?(1, 2, 3)).to be(dbl)
expect_null_double(dbl, dbl.inspect)
expect_null_double(dbl, dbl.itself)
expect_null_double(dbl, dbl.not_nil!)
expect_null_double(dbl, dbl.pretty_inspect)
expect_null_double(dbl, dbl.tap { nil })
expect_null_double(dbl, dbl.to_json)
expect_null_double(dbl, dbl.to_pretty_json)
expect_null_double(dbl, dbl.to_s)
expect_null_double(dbl, dbl.to_yaml)
expect_null_double(dbl, dbl.try { nil })
# expect(dbl.object_id).to be(dbl)
# expect(dbl.same?(dbl)).to be(dbl)
# expect(dbl.same?(nil)).to be(dbl)
end
end
end
context "with arguments constraints" do
let(arguments) { Spectator::Arguments.capture(/foo/) }
context "without common object methods" do
Spectator::NullDouble.define(TestDouble) do
abstract_stub abstract def foo(value) : String
end
let(stub) { Spectator::ValueStub.new(:foo, "bar", arguments).as(Spectator::Stub) }
subject(dbl) { TestDouble.new([stub]) }
it "returns the response when constraint satisfied" do
expect(dbl.foo("foobar")).to eq("bar")
end
it "returns self when constraint unsatisfied" do
expect_null_double(dbl, dbl.foo("baz"))
end
it "returns self when argument count doesn't match" do
expect_null_double(dbl, dbl.foo)
end
it "has a union return type with self" do
expect(dbl.foo("foobar")).to compile_as(String | TestDouble)
end
end
context "with common object methods" do
Spectator::NullDouble.define(TestDouble) do
stub abstract def hash(hasher)
end
let(stub) { Spectator::ValueStub.new(:hash, 12345, arguments).as(Spectator::Stub) }
subject(dbl) { TestDouble.new([stub]) }
it "returns the response when constraint satisfied" do
expect(dbl.hash("foobar")).to eq(true)
end
it "returns self when constraint unsatisfied" do
expect_null_double(dbl, dbl.hash("baz"))
end
it "returns self when argument count doesn't match" do
expect_null_double(dbl, dbl.hash)
end
it "has a union return type with self" do
expect(dbl.hash("foobar")).to compile_as(Int32 | TestDouble)
end
end
end
describe "#_spectator_define_stub" do
subject(dbl) { FooBarDouble.new }
let(stub3) { Spectator::ValueStub.new(:foo, 3) }
let(stub5) { Spectator::ValueStub.new(:foo, 5) }
let(stub7) { Spectator::ValueStub.new(:foo, 7, Spectator::Arguments.capture(:lucky)) }
it "overrides an existing method" do
expect { dbl._spectator_define_stub(stub3) }.to change { dbl.foo }.from(42).to(3)
end
it "replaces an existing stub" do
dbl._spectator_define_stub(stub3)
expect { dbl._spectator_define_stub(stub5) }.to change { dbl.foo }.from(3).to(5)
end
it "doesn't affect other methods" do
expect { dbl._spectator_define_stub(stub5) }.to_not change { dbl.bar }
end
it "picks the correct stub based on arguments" do
dbl._spectator_define_stub(stub5)
dbl._spectator_define_stub(stub7)
aggregate_failures do
expect(dbl.foo).to eq(5)
expect(dbl.foo(:lucky)).to eq(7)
end
end
it "only uses a stub if an argument constraint is met" do
dbl._spectator_define_stub(stub7)
aggregate_failures do
expect(dbl.foo).to eq(42)
expect(dbl.foo(:lucky)).to eq(7)
end
end
end
end

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require "./arguments"
require "./method_call"
require "./stub"
require "./stubbable"
require "./stubbed_name"
require "./unexpected_message"
require "./value_stub"
module Spectator
# Stands in for an object for testing that a SUT calls expected methods.
#
# Handles all messages (method calls), but only responds to those configured.
# Methods called that were not configured will return self.
# Doubles should be defined with the `#define` macro.
#
# Use `#_spectator_define_stub` to override behavior of a method in the double.
# Only methods defined in the double's type can have stubs.
# New methods are not defines when a stub is added that doesn't have a matching method name.
abstract class NullDouble
include Stubbable
Log = Spectator::Log.for(self)
# Defines a test double type.
#
# The *type_name* is the name to give the class.
# Instances of the double can be named by providing a *name*.
# This can be a symbol, string, or even a type.
# See `StubbedName` for details.
#
# After the names, a collection of key-value pairs can be given to quickly define methods.
# Each key is the method name, and the corresponding value is the value returned by the method.
# These methods accept any arguments.
# Additionally, these methods can be overridden later with stubs.
#
# Lastly, a block can be provided to define additional methods and stubs.
# The block is evaluated in the context of the double's class.
#
# ```
# Double.define(SomeDouble, meth1: 42, meth2: "foobar") do
# stub abstract def meth3 : Symbol
# end
# ```
macro define(type_name, name = nil, **value_methods, &block)
{% if name %}@[::Spectator::StubbedName({{name}})]{% end %}
class {{type_name.id}} < {{@type.name}}
{% for key, value in value_methods %}
inject_stub def {{key.id}}(*%args, **%kwargs)
{{value}}
end
{% end %}
{% if block %}{{block.body}}{% end %}
end
end
# Creates the double.
#
# An initial set of *stubs* can be provided.
def initialize(@stubs : Array(Stub) = [] of Stub)
end
# Defines a stub to change the behavior of a method in this double.
#
# NOTE: Defining a stub for a method not defined in the double's type has no effect.
protected def _spectator_define_stub(stub : Stub) : Nil
@stubs.unshift(stub)
end
private def _spectator_find_stub(call : MethodCall) : Stub?
Log.debug { "Finding stub for #{call}" }
stub = @stubs.find &.===(call)
Log.debug { stub ? "Found stub #{stub} for #{call}" : "Did not find stub for #{call}, returning self" }
stub
end
private def _spectator_stubbed_name : String
{% if anno = @type.annotation(StubbedName) %}
"#<NullDouble " + {{(anno[0] || :Anonymous.id).stringify}} + ">"
{% else %}
"#<NullDouble Anonymous>"
{% end %}
end
# "Hide" existing methods and methods from ancestors by overriding them.
macro finished
stub_all {{@type.name(generic_args: false)}}
end
# Handle all methods but only respond to configured messages.
# Returns self.
macro method_missing(_call)
self
end
end
end