test_provider.rb: Run a test requiring the legacy provider conditiona…

…lly.

In some cases, the legacy provider is not installed intentionally. So, we omit a
test requiring the legacy provider if the legacy provider is not loadable.

In the test_openssl_provider_names test, we use base provider instead of legacy
provider, because we would expect the base provider is always loadable in OpenSSL 3
for now.

You can see the list of the standard providers below.
https://wiki.openssl.org/index.php/OpenSSL_3.0#Providers

test/openssl/test_provider.rb

@@ -13,13 +13,13 @@ def test_openssl_provider_name_inspect
 
   def test_openssl_provider_names
     with_openssl <<-'end;'
-      legacy_provider = OpenSSL::Provider.load("legacy")
+      base_provider = OpenSSL::Provider.load("base")
       assert_equal(2, OpenSSL::Provider.provider_names.size)
-      assert_includes(OpenSSL::Provider.provider_names, "legacy")
+      assert_includes(OpenSSL::Provider.provider_names, "base")
 
-      assert_equal(true, legacy_provider.unload)
+      assert_equal(true, base_provider.unload)
       assert_equal(1, OpenSSL::Provider.provider_names.size)
-      assert_not_includes(OpenSSL::Provider.provider_names, "legacy")
+      assert_not_includes(OpenSSL::Provider.provider_names, "base")
     end;
   end
 
@@ -34,7 +34,12 @@ def test_unloaded_openssl_provider
 
   def test_openssl_legacy_provider
     with_openssl(<<-'end;')
-      OpenSSL::Provider.load("legacy")
+      begin
+        OpenSSL::Provider.load("legacy")
+      rescue OpenSSL::Provider::ProviderError
+        omit "Only for OpenSSL with legacy provider"
+      end
+
       algo = "RC4"
       data = "a" * 1000
       key = OpenSSL::Random.random_bytes(16)