1 files changed, 145 insertions, 0 deletions
diff --git a/src/test_helpers/with_view_state.rs b/src/test_helpers/with_view_state.rs
new file mode 100644
index 0000000..c1daf8e
--- /dev/null
+++ b/src/test_helpers/with_view_state.rs
@@ -0,0 +1,145 @@
+use std::time::Duration;
+
+use crate::view::{RenderAction, State, ViewAction};
+
+#[allow(clippy::panic)]
+fn assert_view_state_actions(state: &State, expected_actions: &[String]) {
+	let actions = state
+		.render_slice()
+		.lock()
+		.get_actions()
+		.iter()
+		.map(|a| {
+			match *a {
+				RenderAction::ScrollDown => String::from("ScrollDown"),
+				RenderAction::ScrollUp => String::from("ScrollUp"),
+				RenderAction::ScrollRight => String::from("ScrollRight"),
+				RenderAction::ScrollLeft => String::from("ScrollLeft"),
+				RenderAction::ScrollTop => String::from("ScrollTop"),
+				RenderAction::ScrollBottom => String::from("ScrollBottom"),
+				RenderAction::PageUp => String::from("PageUp"),
+				RenderAction::PageDown => String::from("PageDown"),
+				RenderAction::Resize(width, height) => format!("Resize({width}, {height})"),
+			}
+		})
+		.collect::<Vec<String>>();
+
+	let mut mismatch = false;
+	let mut error_output = vec![
+		String::from("\nUnexpected actions!"),
+		String::from("--- Expected"),
+		String::from("+++ Actual"),
+		String::from("=========="),
+	];
+
+	for (expected_action, actual_action) in expected_actions.iter().zip(actions.iter()) {
+		if expected_action == actual_action {
+			error_output.push(format!(" {expected_action}"));
+		}
+		else {
+			mismatch = true;
+			error_output.push(format!("-{expected_action}"));
+			error_output.push(format!("+{actual_action}"));
+		}
+	}
+
+	match expected_actions.len() {
+		a if a > actions.len() => {
+			mismatch = true;
+			for action in expected_actions.iter().skip(actions.len()) {
+				error_output.push(format!("-{action}"));
+			}
+		},
+		a if a < actions.len() => {
+			mismatch = true;
+			for action in actions.iter().skip(expected_actions.len()) {
+				error_output.push(format!("+{action}"));
+			}
+		},
+		_ => {},
+	}
+
+	if mismatch {
+		error_output.push(String::from("==========\n"));
+		panic!("{}", error_output.join("\n"));
+	}
+}
+
+fn action_to_string(action: ViewAction) -> String {
+	String::from(match action {
+		ViewAction::Stop => "Stop",
+		ViewAction::Refresh => "Refresh",
+		ViewAction::Render => "Render",
+		ViewAction::Start => "Start",
+		ViewAction::End => "End",
+	})
+}
+
+/// Context for a view state test.
+#[derive(Debug)]
+#[non_exhaustive]
+pub(crate) struct ViewStateTestContext {
+	/// The state instance.
+	pub(crate) state: State,
+}
+
+impl ViewStateTestContext {
+	/// Assert that render actions were sent.
+	pub(crate) fn assert_render_action(&self, actions: &[&str]) {
+		assert_view_state_actions(
+			&self.state,
+			actions
+				.iter()
+				.map(|s| String::from(*s))
+				.collect::<Vec<String>>()
+				.as_slice(),
+		);
+	}
+
+	/// Assert that certain messages were sent by the `State`.
+	#[allow(clippy::missing_panics_doc, clippy::panic)]
+	pub(crate) fn assert_sent_messages(&self, messages: Vec<&str>) {
+		let mut mismatch = false;
+		let mut error_output = vec![
+			String::from("\nUnexpected messages!"),
+			String::from("--- Expected"),
+			String::from("+++ Actual"),
+			String::from("=========="),
+		];
+
+		let update_receiver = self.state.update_receiver();
+		for message in messages {
+			if let Ok(action) = update_receiver.recv_timeout(Duration::new(1, 0)) {
+				let action_name = action_to_string(action);
+				if message == action_name {
+					error_output.push(format!(" {message}"));
+				}
+				else {
+					mismatch = true;
+					error_output.push(format!("-{message}"));
+					error_output.push(format!("+{action_name}"));
+				}
+			}
+			else {
+				error_output.push(format!("-{message}"));
+			}
+		}
+
+		// wait some time for any other actions that were sent that should have not been
+		while let Ok(action) = update_receiver.recv_timeout(Duration::new(0, 10000)) {
+			mismatch = true;
+			error_output.push(format!("+{}", action_to_string(action)));
+		}
+
+		if mismatch {
+			error_output.push(String::from("==========\n"));
+			panic!("{}", error_output.join("\n"));
+		}
+	}
+}
+
+/// Provide a `State` instance for use within a view test.
+pub(crate) fn with_view_state<C>(callback: C)
+where C: FnOnce(ViewStateTestContext) {
+	callback(ViewStateTestContext { state: State::new() });
+}