fix upsert tests

Author: tanner0101

Tests/PostgreSQLTests/PostgreSQLConnectionTests.swift

@@ -540,6 +540,21 @@ class PostgreSQLConnectionTests: XCTestCase {
             print(c)
         }
     }
+    
+    func testUpsert() throws {
+        let values: [(PostgreSQLUpsert.Identifier, PostgreSQLUpsert.Expression)] = []
+        
+        var upsert: PostgreSQLUpsert
+        
+        upsert = PostgreSQLUpsert.upsert(nil, values)
+        XCTAssertEqual(upsert.columns, [PostgreSQLColumnIdentifier.column(nil, .identifier("id"))])
+        
+        upsert = PostgreSQLUpsert.upsert([], values)
+        XCTAssertEqual(upsert.columns, [PostgreSQLColumnIdentifier.column(nil, .identifier("id"))])
+        
+        upsert = PostgreSQLUpsert.upsert([.column(nil, .identifier("field"))], values)
+        XCTAssertEqual(upsert.columns, [PostgreSQLColumnIdentifier.column(nil, .identifier("field"))])
+    }
 
     static var allTests = [
         ("testBenchmark", testBenchmark),
@@ -560,6 +575,7 @@ class PostgreSQLConnectionTests: XCTestCase {
         ("testOrderBy", testOrderBy),
         ("testInvalidDate", testInvalidDate),
         ("testEmptyArray", testEmptyArray),
+        ("testUpsert", testUpsert),
     ]
 }