Fix typos (#57)

Author: pirj

README.md

@@ -139,7 +139,7 @@ If you still get lock timeout while adding / removing indexes, it might be for o
 
 </details>
 
-<details><summary id="safe_add_foreign_key">safe <code>add_foreign_key</code> (and <code>add_reference</code>)</summary>
+<details><summary id="safe_add_foreign_key">Safe <code>add_foreign_key</code> (and <code>add_reference</code>)</summary>
 
 Adding a foreign key requires a `SHARE ROW EXCLUSIVE` lock, which **prevent writing in the tables** while the migration is running.
 

test/add_foreign_key_test.rb

@@ -2,7 +2,7 @@
 
 require 'test_helper'
 
-class AddForeignKeyTest < MiniTest::Test
+class AddForeignKeyTest < Minitest::Test
   DUMMY_MIGRATION_VERSION = 8128
 
   def setup

test/create_table_test.rb

@@ -2,7 +2,7 @@
 
 require 'test_helper'
 
-class SafePgMigrationsTest < Minitest::Test
+class CreateTableTest < Minitest::Test
   def setup
     SafePgMigrations.instance_variable_set(:@config, nil)
     @connection = ActiveRecord::Base.connection

test/useless_statement_logger_test.rb

@@ -2,7 +2,7 @@
 
 require 'test_helper'
 
-class UselessStatementLoggerTest < MiniTest::Unit::TestCase
+class UselessStatementLoggerTest < Minitest::Test
   def setup
     SafePgMigrations.instance_variable_set(:@config, nil)
     @connection = ActiveRecord::Base.connection