Change AssertEmptyLiteral cop to check for assert_equal

While this cop is correct that we should be using `assert_empty(list)`
over `assert([], list)`, it's right for the wrong reasons. That example
is bad because it's using `assert` and not `assert_equal`. An empty
list/hash is truthy so the assertion will always succeed. That is,
`assert([], [1, 2, 3])` will succeed even though at a glance it looks
like it shouldn't. I believe that what this cop is intending to check
for is `assert_equal([], list)` instead so I've updated the references
to `assert` to `assert_equal`.

Issue rubocop#117 proposes that we try to detect when `assert` is used where
the user likely wanted `assert_equal` so while this cop will no longer
register a violation for `assert([], list)`, if that proposal is
accepted then a future cop *will* register a violation.

lib/rubocop/cop/minitest/assert_empty_literal.rb

@@ -4,12 +4,12 @@ module RuboCop
   module Cop
     module Minitest
       # This cop enforces the test to use `assert_empty`
-      # instead of using `assert([], object)`.
+      # instead of using `assert_equal([], object)`.
       #
       # @example
       #   # bad
-      #   assert([], object)
-      #   assert({}, object)
+      #   assert_equal([], object)
+      #   assert_equal({}, object)
       #
       #   # good
       #   assert_empty(object)
@@ -18,14 +18,14 @@ class AssertEmptyLiteral < Cop
         include ArgumentRangeHelper
 
         MSG = 'Prefer using `assert_empty(%<arguments>s)` over ' \
-              '`assert(%<literal>s, %<arguments>s)`.'
+              '`assert_equal(%<literal>s, %<arguments>s)`.'
 
-        def_node_matcher :assert_with_empty_literal, <<~PATTERN
-          (send nil? :assert ${hash array} $...)
+        def_node_matcher :assert_equal_with_empty_literal, <<~PATTERN
+          (send nil? :assert_equal ${hash array} $...)
         PATTERN
 
         def on_send(node)
-          assert_with_empty_literal(node) do |literal, matchers|
+          assert_equal_with_empty_literal(node) do |literal, matchers|
             return unless literal.values.empty?
 
             args = matchers.map(&:source).join(', ')
@@ -36,7 +36,7 @@ def on_send(node)
         end
 
         def autocorrect(node)
-          assert_with_empty_literal(node) do |_literal, matchers|
+          assert_equal_with_empty_literal(node) do |_literal, matchers|
             object = matchers.first
 
             lambda do |corrector|

test/rubocop/cop/minitest/assert_empty_literal_test.rb

@@ -7,8 +7,8 @@ def test_registers_offense_when_asserting_empty_array
     assert_offense(<<~RUBY)
       class FooTest < Minitest::Test
         def test_do_something
-          assert([], somestuff)
-          ^^^^^^^^^^^^^^^^^^^^^ Prefer using `assert_empty(somestuff)` over `assert([], somestuff)`.
+          assert_equal([], somestuff)
+          ^^^^^^^^^^^^^^^^^^^^^^^^^^^ Prefer using `assert_empty(somestuff)` over `assert_equal([], somestuff)`.
         end
       end
     RUBY
@@ -26,8 +26,8 @@ def test_registers_offense_when_asserting_empty_hash
     assert_offense(<<~RUBY)
       class FooTest < Minitest::Test
         def test_do_something
-          assert({}, somestuff)
-          ^^^^^^^^^^^^^^^^^^^^^ Prefer using `assert_empty(somestuff)` over `assert({}, somestuff)`.
+          assert_equal({}, somestuff)
+          ^^^^^^^^^^^^^^^^^^^^^^^^^^^ Prefer using `assert_empty(somestuff)` over `assert_equal({}, somestuff)`.
         end
       end
     RUBY
@@ -41,7 +41,7 @@ def test_do_something
     RUBY
   end
 
-  def test_does_not_register_offense_when_using_assert_equal
+  def test_does_not_register_offense_when_asserting_non_empty_array
     assert_no_offenses(<<~RUBY)
       class FooTest < Minitest::Test
         def test_do_something
@@ -51,11 +51,11 @@ def test_do_something
     RUBY
   end
 
-  def test_does_not_register_offense_when_using_assert_with_single_parameter
+  def test_does_not_register_offense_when_asserting_two_parameters
     assert_no_offenses(<<~RUBY)
       class FooTest < Minitest::Test
         def test_do_something
-          assert(somestuff)
+          assert_equal(somestuff, someotherstuff)
         end
       end
     RUBY