Don't attempt to specify datetime precision unless supported

Specifically, versions of MySQL prior to 5.6 do not support this, which
is what's used on Travis by default. The method `mysql_56?` appeared to
only ever be used to conditionally apply subsecond precision, so I've
generalized it and used it more liberally.

This should fix the test failures caused by #20317

2 files changed, 5 insertions, 5 deletions

diff --git a/activerecord/test/cases/base_test.rb b/activerecord/test/cases/base_test.rb
index 3aa0849cb5..991145bed4 100644
--- a/activerecord/test/cases/base_test.rb
+++ b/activerecord/test/cases/base_test.rb
@@ -204,7 +204,7 @@ class BasicsTest < ActiveRecord::TestCase
     )
 
     # For adapters which support microsecond resolution.
-    if current_adapter?(:PostgreSQLAdapter, :SQLite3Adapter) || mysql_56?
+    if subsecond_precision_supported?
       assert_equal 11, Topic.find(1).written_on.sec
       assert_equal 223300, Topic.find(1).written_on.usec
       assert_equal 9900, Topic.find(2).written_on.usec
diff --git a/activerecord/test/cases/helper.rb b/activerecord/test/cases/helper.rb
index b61a5126e0..8773986882 100644
--- a/activerecord/test/cases/helper.rb
+++ b/activerecord/test/cases/helper.rb
@@ -46,10 +46,10 @@ def in_memory_db?
   ActiveRecord::Base.connection_pool.spec.config[:database] == ":memory:"
 end
 
-def mysql_56?
-  current_adapter?(:MysqlAdapter, :Mysql2Adapter) &&
-    ActiveRecord::Base.connection.send(:version) >= '5.6.0' &&
-    ActiveRecord::Base.connection.send(:version) < '5.7.0'
+def subsecond_precision_supported?
+  !current_adapter?(:MysqlAdapter, :Mysql2Adapter) ||
+    (ActiveRecord::Base.connection.send(:version) >= '5.6.0' &&
+    ActiveRecord::Base.connection.send(:version) < '5.7.0')
 end
 
 def mysql_enforcing_gtid_consistency?