Add Select Expression Tests

Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

Tests/p4rseTests/ExpressionTests/SelectExpression.swift

@@ -0,0 +1,139 @@
+// p4rse, Copyright 2026, Will Hawkins
+//
+// This file is part of p4rse.
+//
+// This file is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program. If not, see <https://www.gnu.org/licenses/>.
+
+import Common
+import Foundation
+import Macros
+import P4Lang
+import P4Runtime
+import SwiftTreeSitter
+import Testing
+import TreeSitter
+import TreeSitterP4
+
+@testable import P4Compiler
+
+@Test func test_simple_parser_with_transition_select_case_nondefault_expressions() async throws {
+  let simple_parser_declaration = """
+      parser main_parser() {
+        state start {
+          transition select (true) {
+            false: reject;
+            true: accept;
+          };
+        }
+      };
+    """
+
+  let program = try #UseOkResult(Program.Compile(simple_parser_declaration))
+  let parser = try #UseOkResult(program.find_parser(withName: Identifier(name: "main_parser")))
+  let runtime = try #UseOkResult(P4Runtime.ParserRuntime.create(program: program))
+  let (state_result, _) = try! #UseOkResult(runtime.run())
+
+  #expect(parser.states.count() == 1)
+
+  #expect(AsInstantiatedParserState(state_result) == P4Lang.accept)
+}
+
+@Test func test_simple_parser_with_transition_select_case_default_expression() async throws {
+  let simple_parser_declaration = """
+      parser main_parser() {
+        state start {
+          transition select (5) {
+            5: reject;
+            _: accept;
+          };
+        }
+      };
+    """
+
+  let program = try #UseOkResult(Program.Compile(simple_parser_declaration))
+  let parser = try #UseOkResult(program.find_parser(withName: Identifier(name: "main_parser")))
+  let runtime = try #UseOkResult(P4Runtime.ParserRuntime.create(program: program))
+  let (state_result, _) = try! #UseOkResult(runtime.run())
+
+  #expect(parser.states.count() == 1)
+
+  #expect(AsInstantiatedParserState(state_result) == P4Lang.reject)
+}
+
+@Test func test_simple_parser_with_transition_select_case_default_expression2() async throws {
+  let simple_parser_declaration = """
+      parser main_parser() {
+        state start {
+          transition select (1) {
+            5: reject;
+            _: accept;
+          };
+        }
+      };
+    """
+
+  let program = try #UseOkResult(Program.Compile(simple_parser_declaration))
+  let parser = try #UseOkResult(program.find_parser(withName: Identifier(name: "main_parser")))
+  let runtime = try #UseOkResult(P4Runtime.ParserRuntime.create(program: program))
+  let (state_result, _) = try! #UseOkResult(runtime.run())
+
+  #expect(parser.states.count() == 1)
+
+  #expect(AsInstantiatedParserState(state_result) == P4Lang.accept)
+}
+
+@Test func test_simple_parser_with_transition_select_case_default_expression3() async throws {
+  let simple_parser_declaration = """
+      parser main_parser() {
+        state start {
+          transition select (6) {
+            5: reject;
+            6: reject;
+            _: accept;
+          };
+        }
+      };
+    """
+
+  let program = try #UseOkResult(Program.Compile(simple_parser_declaration))
+  let parser = try #UseOkResult(program.find_parser(withName: Identifier(name: "main_parser")))
+  let runtime = try #UseOkResult(P4Runtime.ParserRuntime.create(program: program))
+  let (state_result, _) = try! #UseOkResult(runtime.run())
+
+  #expect(parser.states.count() == 1)
+
+  #expect(AsInstantiatedParserState(state_result) == P4Lang.reject)
+}
+
+@Test func test_simple_parser_with_transition_select_case_invalid_type() async throws {
+  let simple_parser_declaration = """
+      parser main_parser() {
+        state start {
+          transition select (6) {
+            true: reject;
+            6: reject;
+            _: accept;
+          };
+        }
+      };
+    """
+
+  #expect(
+    #RequireErrorResult(
+      Error(
+        withMessage:
+        "Error(s) parsing select cases: {81, 12}: Keyset expression type does not match selector expression type"
+      ),
+      Program.Compile(simple_parser_declaration)))
+}