Add initial auto_bounds test for Plot (#220)

Includes the following changes:
- Add `egui_kittest`, `log`, `env_logger`, `assertables` as
dev-dependencies to egui_plot crate
- Add test-only `init_test_logger` function to enable capturing
`log::info!` and friends in tests
- Add tests for basic auto_bounds behavior to be an example for
additional test cases

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* Closes <#219>
* [x] I have followed the instructions in the PR template

---------

Co-authored-by: Michal Sustr <michal.sustr@gmail.com>

Author: kitizz

Cargo.lock

@@ -303,6 +303,12 @@ dependencies = [
  "zbus",
 ]
 
+[[package]]
+name = "assertables"
+version = "9.8.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "59051ec02907378a67b0ba1b8631121f5388c8dbbb3cec8c749d8f93c2c3c211"
+
 [[package]]
 name = "async-broadcast"
 version = "0.7.2"
@@ -1192,9 +1198,13 @@ name = "egui_plot"
 version = "0.34.0"
 dependencies = [
  "ahash",
+ "assertables",
  "document-features",
  "egui",
+ "egui_kittest",
  "emath",
+ "env_logger",
+ "log",
  "serde",
 ]
 

Cargo.toml

@@ -45,6 +45,7 @@ ahash = { version = "0.8.12", default-features = false, features = [
     "no-rng", # we don't need DOS-protection, so we let users opt-in to it instead
     "std",
 ] }
+assertables = "9.8.2"
 document-features = "0.2.12"
 eframe = { version = "0.33", default-features = false }
 egui = { version = "0.33", default-features = false }
@@ -279,3 +280,7 @@ zero_sized_map_values = "warn"
 
 manual_range_contains = "allow" # this is better on 'allow'
 map_unwrap_or = "allow"         # this is better on 'allow'
+
+
+[workspace.metadata.cargo-shear]
+ignored = ["log", "assertables"]

egui_plot/Cargo.toml

@@ -45,3 +45,9 @@ ahash.workspace = true
 document-features = { workspace = true, optional = true }
 
 serde = { workspace = true, optional = true }
+
+[dev-dependencies]
+assertables.workspace = true
+egui_kittest.workspace = true
+env_logger.workspace = true
+log.workspace = true

egui_plot/src/plot.rs

@@ -2124,3 +2124,44 @@ impl<'a> PlotUi<'a> {
         self.items.push(Box::new(heatmap));
     }
 }
+
+#[cfg(all(test, not(target_arch = "wasm32")))]
+mod plot_tests {
+    use super::*;
+    use crate::{Plot, Points};
+
+    use egui_kittest::Harness;
+
+    /// Test that `auto_bounds(true)` fits the data exactly when the margin fraction is zero.
+    #[test]
+    fn auto_bounds_true() {
+        crate::utils::init_test_logger();
+
+        const MIN: [f64; 2] = [-10.0, -10.0];
+        const MAX: [f64; 2] = [10.0, 10.0];
+
+        let harness = {
+            let bounds = PlotBounds::from_min_max(MIN, MAX);
+            Harness::new_ui_state(
+                |ui, bounds| {
+                    let plot = Plot::new("test_plot")
+                        .auto_bounds(true)
+                        .set_margin_fraction(Vec2::splat(0.0));
+
+                    plot.show(ui, |plot_ui| {
+                        let corners = vec![MIN, MAX];
+                        plot_ui.points(Points::new("filler", corners));
+                        *bounds = plot_ui.plot_bounds();
+                    });
+                },
+                bounds,
+            )
+        };
+
+        let final_bounds = harness.state();
+        assert!((final_bounds.min[0] - MIN[0]).abs() <= f64::EPSILON);
+        assert!((final_bounds.min[1] - MIN[1]).abs() <= f64::EPSILON);
+        assert!((final_bounds.max[0] - MAX[0]).abs() <= f64::EPSILON);
+        assert!((final_bounds.max[1] - MAX[1]).abs() <= f64::EPSILON);
+    }
+}

egui_plot/src/utils.rs

@@ -56,3 +56,39 @@ pub(crate) fn find_name_candidate(name: &str, width: f32, painter: &Painter, fon
 
     best
 }
+
+/// Initialize logging so that the testing framework can capture log output.
+///
+/// Call this at the top of a test function to see log output from that test.
+/// The logging output will only be shown when the following conditions are met:
+/// - The test fails
+/// - The `RUST_LOG` environment variable is set to a level at or below the message level
+///
+/// When running a specific test:
+/// ```sh
+/// RUST_LOG=info cargo test auto_bounds_true
+/// ```
+///
+/// If the something causes the test to panic so hard that it never shows logging output,
+/// you can use `--nocapture` to see log output as it happens:
+/// ```sh
+/// RUST_LOG=info cargo test auto_bounds_true -- --nocapture
+/// ```
+#[cfg(test)]
+pub(crate) fn init_test_logger() {
+    use std::io::Write as _;
+    let _result: Result<(), log::SetLoggerError> = env_logger::builder()
+        .is_test(true)
+        .format(|buf, record| {
+            let level_style = buf.default_level_style(record.level());
+            writeln!(
+                buf,
+                "[{level_style}{}{level_style:#} {}:{}]   {}",
+                record.level(),
+                record.file().unwrap_or("unknown"),
+                record.line().unwrap_or(0),
+                record.args()
+            )
+        })
+        .try_init();
+}