diff --git a/.github/workflows/rust.yml b/.github/workflows/rust.yml
index 8a90d20..2657a81 100644
--- a/.github/workflows/rust.yml
+++ b/.github/workflows/rust.yml
@@ -13,21 +13,31 @@ env:
 jobs:
   build:
     runs-on: ${{matrix.os}}
+    env:
+      DISPLAY: ':99'
     strategy:
       fail-fast: false
       matrix: 
         os: [macos-latest, ubuntu-latest, windows-latest]
+        include:
+        - os: ubuntu-latest
+          headless: Xvfb :99 -screen 0 1024x768x24 > /dev/null 2>&1 &
 
     steps:
       - uses: actions/checkout@v3
       - uses: Swatinem/rust-cache@v2
-
+        with:
+          # To only cache runs from `master`
+          save-if: ${{ github.ref == 'refs/heads/main' }}
       - if: matrix.os == 'ubuntu-latest'
         uses: awalsh128/cache-apt-pkgs-action@latest
         with:
           packages: libxtst-dev libevdev-dev libxdo-dev
           version: 1.0
 
+      - name: Setup headless environment
+        run: ${{matrix.headless}}
+
       - name: Add components
         run: rustup component add clippy rustfmt
 
diff --git a/src/lib.rs b/src/lib.rs
index 43a4812..0003e63 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -453,3 +453,59 @@ impl Frontend for Wish {
         self.predicates_widget.text(&texts.join("\n"));
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use crate::{Config, Wish};
+    use afrim::frontend::Frontend;
+    use std::path::Path;
+    use std::thread;
+    use std::time::Duration;
+
+    #[test]
+    fn test_api() {
+        let config = Config::from_file(Path::new("data/full_sample.toml")).unwrap();
+        let mut afrim_wish = Wish::init(config);
+        afrim_wish.build();
+
+        // Test without data.
+        afrim_wish.clear_predicates();
+        afrim_wish.next_predicate();
+        afrim_wish.previous_predicate();
+        assert!(afrim_wish.get_selected_predicate().is_none());
+        afrim_wish.display();
+
+        // Test the adding of predicates.
+        afrim_wish.set_page_size(3);
+        afrim_wish.set_input("Test started!");
+        afrim_wish.add_predicate("test", "123", "ok");
+        afrim_wish.add_predicate("test1", "23", "ok");
+        afrim_wish.add_predicate("test12", "1", "ok");
+        afrim_wish.add_predicate("test123", "", "ok");
+        afrim_wish.add_predicate("test1234", "", "");
+        afrim_wish.display();
+
+        // Test the geometry.
+        (0..100).for_each(|i| {
+            if i % 10 != 0 {
+                return;
+            };
+            let i = i as f64;
+            afrim_wish.update_position((i, i));
+            thread::sleep(Duration::from_millis(100));
+        });
+
+        // Test the navigation.
+        afrim_wish.previous_predicate();
+        assert_eq!(
+            afrim_wish.get_selected_predicate(),
+            Some(&("test1234".to_owned(), "".to_owned(), "".to_owned()))
+        );
+        afrim_wish.next_predicate();
+        assert_eq!(
+            afrim_wish.get_selected_predicate(),
+            Some(&("test".to_owned(), "123".to_owned(), "ok".to_owned()))
+        );
+        afrim_wish.display();
+    }
+}