Add tests for ArgumentParser::get

These test the API shown in README.md, rather than the Argument::get
function that does most of the work.

Signed-off-by: Sean Robinson <sean.robinson@scottsdalecc.edu>

test/CMakeLists.txt

@@ -30,6 +30,7 @@ file(GLOB ARGPARSE_TEST_SOURCES
     test_compound_arguments.cpp
     test_container_arguments.cpp
     test_const_correct.cpp
+    test_get.cpp
     test_help.cpp
     test_invalid_arguments.cpp
     test_is_used.cpp

test/test_get.cpp

@@ -0,0 +1,29 @@
+#include <doctest.hpp>
+#include <argparse/argparse.hpp>
+
+using doctest::test_suite;
+
+TEST_CASE("Getting a simple argument" * test_suite("ArgumentParser::get")) {
+  argparse::ArgumentParser program("test");
+  program.add_argument("-s", "--stuff");
+  REQUIRE_NOTHROW(program.parse_args({ "test", "-s", "./src" }));
+  REQUIRE(program.get("--stuff") == "./src");
+}
+
+TEST_CASE("Missing argument" * test_suite("ArgumentParser::get")) {
+  argparse::ArgumentParser program("test");
+  program.add_argument("-s", "--stuff");
+  REQUIRE_NOTHROW(program.parse_args({ "test" }));
+  REQUIRE_THROWS_WITH_AS(program.get("--stuff"),
+                         "No value provided",
+                         std::logic_error);
+}
+
+TEST_CASE("Implicit argument" * test_suite("ArgumentParser::get")) {
+  argparse::ArgumentParser program("test");
+  program.add_argument("-s", "--stuff").nargs(1);
+  REQUIRE_NOTHROW(program.parse_args({ "test" }));
+  REQUIRE_THROWS_WITH_AS(program.get("--stuff"),
+                         "No value provided",
+                         std::logic_error);
+}