diff --git a/.github/workflows/ci.pinnacle.yml b/.github/workflows/ci.pinnacle.yml
index 847a871..51b8b13 100644
--- a/.github/workflows/ci.pinnacle.yml
+++ b/.github/workflows/ci.pinnacle.yml
@@ -53,10 +53,10 @@ jobs:
         uses: leafo/gh-actions-luarocks@v4
       - name: Build
         if: ${{ runner.debug != '1' }}
-        run: cargo test
+        run: cargo test -- --test-threads=1
       - name: Build (debug)
         if: ${{ runner.debug == '1' }}
-        run: RUST_LOG=debug cargo test -- --nocapture
+        run: RUST_LOG=debug cargo test -- --nocapture --test-threads=1
   check-format:
     runs-on: ubuntu-latest
     name: Check formatting
@@ -79,6 +79,8 @@ jobs:
         uses: dtolnay/rust-toolchain@stable
         with:
           components: clippy
+      - name: Cache stuff
+        uses: Swatinem/rust-cache@v2
       - name: Get dependencies
         run: sudo apt update && sudo apt install libwayland-dev libxkbcommon-dev libudev-dev libinput-dev libgbm-dev libseat-dev libsystemd-dev protobuf-compiler xwayland libegl-dev
       - name: Setup Lua
diff --git a/api/lua/pinnacle/window.lua b/api/lua/pinnacle/window.lua
index bc594ac..73ae610 100644
--- a/api/lua/pinnacle/window.lua
+++ b/api/lua/pinnacle/window.lua
@@ -224,7 +224,7 @@ local _fullscreen_or_maximized_keys = {
 --- -- A simple window rule. This one will cause Firefox to open on tag "Browser".
 ---Window.add_window_rule({
 ---    cond = { classes = { "firefox" } },
----    rule = { tags = { "Browser" } },
+---    rule = { tags = { Tag.get("Browser") } },
 ---})
 ---
 --- -- To apply rules when *all* provided conditions are true, use `all`.
@@ -234,8 +234,8 @@ local _fullscreen_or_maximized_keys = {
 ---    cond = {
 ---        all = {
 ---            {
----                class = "steam",
----                tag = Tag:get("5"),
+---                classes = { "steam" },
+---                tags = { Tag.get("5") },
 ---            }
 ---        }
 ---    },
@@ -246,8 +246,8 @@ local _fullscreen_or_maximized_keys = {
 --- -- Thus, the above can be shortened to:
 ---Window.add_window_rule({
 ---    cond = {
----        class = "steam",
----        tag = Tag:get("5"),
+---        classes = { "steam" },
+---        tags = { Tag.get("5") },
 ---    },
 ---    rule = { fullscreen_or_maximized = "fullscreen" },
 ---})
@@ -268,17 +268,17 @@ local _fullscreen_or_maximized_keys = {
 ---    cond = {
 ---        all = { -- This `all` block is needed because the outermost block cannot be an array.
 ---            { any = {
----                { class = { "firefox", "thunderbird", "discord" } }
+---                { classes = { "firefox", "thunderbird", "discord" } }
 ---            } },
 ---            { any = {
 ---                -- Because `tag` is inside an `all` block,
 ---                -- the window must have all these tags for this to be true.
 ---                -- If it was in an `any` block, only one tag would need to match.
 ---                { all = {
----                    { tag = { "A", "B", "C" } }
+---                    { tags = { Tag.get("A"), Tag.get("B"), Tag.get("C") } }
 ---                } },
 ---                { all = {
----                    { tag = { "1", "2" } }
+---                    { tags = { Tag.get("1"), Tag.get("2") } }
 ---                } },
 ---            } }
 ---        }
diff --git a/src/cli.rs b/src/cli.rs
index 4173574..94b89dd 100644
--- a/src/cli.rs
+++ b/src/cli.rs
@@ -412,6 +412,8 @@ fn generate_config(args: ConfigGen) -> anyhow::Result<()> {
 
 #[cfg(test)]
 mod tests {
+    use anyhow::Context;
+
     use super::*;
 
     // TODO: find a way to test the interactive bits programmatically
@@ -428,9 +430,7 @@ mod tests {
             "--lang",
             "rust",
             "--dir",
-            temp_dir
-                .to_str()
-                .ok_or(anyhow::anyhow!("not valid unicode"))?,
+            temp_dir.to_str().context("not valid unicode")?,
             "--non-interactive",
         ]);
 
diff --git a/src/window/rules.rs b/src/window/rules.rs
index c32754f..8e5004d 100644
--- a/src/window/rules.rs
+++ b/src/window/rules.rs
@@ -14,7 +14,7 @@ use std::num::NonZeroU32;
 
 use crate::{output::OutputName, tag::TagId, window::window_state::FullscreenOrMaximized};
 
-#[derive(Debug, Clone, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
+#[derive(Debug, Clone, PartialEq, Eq, serde::Serialize, serde::Deserialize, Default)]
 pub struct WindowRuleCondition {
     /// This condition is met when any of the conditions provided is met.
     #[serde(default)]
@@ -137,7 +137,7 @@ impl WindowRuleCondition {
     }
 }
 
-#[derive(Debug, Clone, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
+#[derive(Debug, Clone, PartialEq, Eq, serde::Serialize, serde::Deserialize, Default)]
 pub struct WindowRule {
     /// Set the output the window will open on.
     #[serde(default)]
diff --git a/tests/lua_api.rs b/tests/lua_api.rs
index 7b6ee80..a2c6588 100644
--- a/tests/lua_api.rs
+++ b/tests/lua_api.rs
@@ -1,10 +1,14 @@
 use std::{
     io::Write,
+    panic::UnwindSafe,
     process::{Command, Stdio},
     time::Duration,
 };
 
-use pinnacle::{backend::dummy::setup_dummy, state::State};
+use pinnacle::{
+    backend::dummy::setup_dummy,
+    state::{State, WithState},
+};
 use smithay::reexports::calloop::{
     self,
     channel::{Event, Sender},
@@ -13,21 +17,35 @@ use smithay::reexports::calloop::{
 use test_log::test;
 
 fn run_lua(ident: &str, code: &str) {
-    let code = format!(r#"require("pinnacle").setup(function({ident}) {code} end)"#);
+    #[rustfmt::skip]
+    let code = format!(r#"
+        require("pinnacle").setup(function({ident})
+            local run = function({ident})
+                {code}
+            end
+
+            local success, err = pcall(run, {ident})
+
+            if not success then
+                print(err)
+                os.exit(1)
+            end
+        end)
+    "#);
 
     let mut child = Command::new("lua").stdin(Stdio::piped()).spawn().unwrap();
 
-    let mut stdin = child
-        .stdin
-        .take()
-        .ok_or_else(|| anyhow::anyhow!("failed to open child stdin"))
-        .unwrap();
+    let mut stdin = child.stdin.take().unwrap();
 
     stdin.write_all(code.as_bytes()).unwrap();
 
     drop(stdin);
 
-    child.wait().unwrap();
+    let exit_status = child.wait().unwrap();
+
+    if exit_status.code().is_some_and(|code| code != 0) {
+        panic!("lua code panicked");
+    }
 }
 
 #[allow(clippy::type_complexity)]
@@ -49,7 +67,7 @@ macro_rules! run_lua {
 }
 
 fn test_lua_api(
-    test: impl FnOnce(Sender<Box<dyn FnOnce(&mut State) + Send>>) + Send + 'static,
+    test: impl FnOnce(Sender<Box<dyn FnOnce(&mut State) + Send>>) + Send + UnwindSafe + 'static,
 ) -> anyhow::Result<()> {
     let (mut state, mut event_loop) = setup_dummy(true, None)?;
 
@@ -59,7 +77,7 @@ fn test_lua_api(
         .handle()
         .insert_source(recv, |event, _, state| match event {
             Event::Msg(f) => f(state),
-            Event::Closed => panic!(),
+            Event::Closed => (),
         })
         .map_err(|_| anyhow::anyhow!("failed to insert source"))?;
 
@@ -67,7 +85,17 @@ fn test_lua_api(
 
     state.start_grpc_server(tempdir.path())?;
 
-    std::thread::spawn(move || test(sender));
+    let loop_signal = event_loop.get_signal();
+
+    let join_handle = std::thread::spawn(move || {
+        let res = std::panic::catch_unwind(|| {
+            test(sender);
+        });
+        loop_signal.stop();
+        if let Err(err) = res {
+            std::panic::resume_unwind(err);
+        }
+    });
 
     event_loop.run(None, &mut state, |state| {
         state.fixup_z_layering();
@@ -88,15 +116,277 @@ fn test_lua_api(
         );
     })?;
 
+    if let Err(err) = join_handle.join() {
+        panic!("{err:?}");
+    }
+
     Ok(())
 }
 
+mod coverage {
+    use pinnacle::{
+        tag::TagId,
+        window::{
+            rules::{WindowRule, WindowRuleCondition},
+            window_state::FullscreenOrMaximized,
+        },
+    };
+
+    use super::*;
+
+    // Process
+
+    #[tokio::main]
+    #[self::test]
+    async fn process_spawn() -> anyhow::Result<()> {
+        test_lua_api(|sender| {
+            run_lua! { |Pinnacle|
+                Pinnacle.process.spawn("foot")
+            }
+
+            sleep_secs(1);
+
+            assert(&sender, |state| {
+                assert_eq!(state.windows.len(), 1);
+                assert_eq!(state.windows[0].class(), Some("foot".to_string()));
+            });
+        })
+    }
+
+    #[tokio::main]
+    #[self::test]
+    async fn process_set_env() -> anyhow::Result<()> {
+        test_lua_api(|sender| {
+            run_lua! { |Pinnacle|
+                Pinnacle.process.set_env("PROCESS_SET_ENV", "env value")
+            }
+
+            sleep_secs(1);
+
+            assert(&sender, |_state| {
+                assert_eq!(
+                    std::env::var("PROCESS_SET_ENV"),
+                    Ok("env value".to_string())
+                );
+            });
+        })
+    }
+
+    // Window
+
+    #[tokio::main]
+    #[self::test]
+    async fn window_get_all() -> anyhow::Result<()> {
+        test_lua_api(|_sender| {
+            run_lua! { |Pinnacle|
+                assert(#Pinnacle.window.get_all() == 0)
+
+                for i = 1, 5 do
+                    Pinnacle.process.spawn("foot")
+                end
+            }
+
+            sleep_secs(1);
+
+            run_lua! { |Pinnacle|
+                assert(#Pinnacle.window.get_all() == 5)
+            }
+        })
+    }
+
+    #[tokio::main]
+    #[self::test]
+    async fn window_get_focused() -> anyhow::Result<()> {
+        test_lua_api(|_sender| {
+            run_lua! { |Pinnacle|
+                assert(not Pinnacle.window.get_focused())
+
+                Pinnacle.tag.add(Pinnacle.output.get_focused(), "1")[1]:set_active(true)
+                Pinnacle.process.spawn("foot")
+            }
+
+            sleep_secs(1);
+
+            run_lua! { |Pinnacle|
+                assert(Pinnacle.window.get_focused())
+            }
+        })
+    }
+
+    #[tokio::main]
+    #[self::test]
+    async fn window_add_window_rule() -> anyhow::Result<()> {
+        test_lua_api(|sender| {
+            run_lua! { |Pinnacle|
+                Pinnacle.tag.add(Pinnacle.output.get_focused(), "Tag Name")
+                Pinnacle.window.add_window_rule({
+                    cond = { classes = { "firefox" } },
+                    rule = { tags = { Pinnacle.tag.get("Tag Name") } },
+                })
+            }
+
+            sleep_secs(1);
+
+            assert(&sender, |state| {
+                assert_eq!(state.config.window_rules.len(), 1);
+                assert_eq!(
+                    state.config.window_rules[0],
+                    (
+                        WindowRuleCondition {
+                            class: Some(vec!["firefox".to_string()]),
+                            ..Default::default()
+                        },
+                        WindowRule {
+                            tags: Some(vec![TagId::Some(0)]),
+                            ..Default::default()
+                        }
+                    )
+                );
+            });
+
+            run_lua! { |Pinnacle|
+                Pinnacle.tag.add(Pinnacle.output.get_focused(), "Tag Name 2")
+                Pinnacle.window.add_window_rule({
+                    cond = {
+                        all = {
+                            {
+                                classes = { "steam" },
+                                tags = {
+                                    Pinnacle.tag.get("Tag Name"),
+                                    Pinnacle.tag.get("Tag Name 2"),
+                                },
+                            }
+                        }
+                    },
+                    rule = { fullscreen_or_maximized = "fullscreen" },
+                })
+            }
+
+            sleep_secs(1);
+
+            assert(&sender, |state| {
+                assert_eq!(state.config.window_rules.len(), 2);
+                assert_eq!(
+                    state.config.window_rules[1],
+                    (
+                        WindowRuleCondition {
+                            cond_all: Some(vec![WindowRuleCondition {
+                                class: Some(vec!["steam".to_string()]),
+                                tag: Some(vec![TagId::Some(0), TagId::Some(1)]),
+                                ..Default::default()
+                            }]),
+                            ..Default::default()
+                        },
+                        WindowRule {
+                            fullscreen_or_maximized: Some(FullscreenOrMaximized::Fullscreen),
+                            ..Default::default()
+                        }
+                    )
+                );
+            });
+        })
+    }
+
+    // TODO: window_begin_move
+    // TODO: window_begin_resize
+
+    // WindowHandle
+
+    #[tokio::main]
+    #[self::test]
+    async fn window_handle_close() -> anyhow::Result<()> {
+        test_lua_api(|sender| {
+            run_lua! { |Pinnacle|
+                Pinnacle.process.spawn("foot")
+            }
+
+            sleep_secs(1);
+
+            assert(&sender, |state| {
+                assert_eq!(state.windows.len(), 1);
+            });
+
+            run_lua! { |Pinnacle|
+                Pinnacle.window.get_all()[1]:close()
+            }
+
+            sleep_secs(1);
+
+            assert(&sender, |state| {
+                assert_eq!(state.windows.len(), 0);
+            });
+        })
+    }
+
+    #[tokio::main]
+    #[self::test]
+    async fn window_handle_move_to_tag() -> anyhow::Result<()> {
+        test_lua_api(|sender| {
+            run_lua! { |Pinnacle|
+                local tags = Pinnacle.tag.add(Pinnacle.output.get_focused(), "1", "2", "3")
+                tags[1]:set_active(true)
+                tags[2]:set_active(true)
+                Pinnacle.process.spawn("foot")
+            }
+
+            sleep_secs(1);
+
+            assert(&sender, |state| {
+                assert_eq!(
+                    state.windows[0].with_state(|st| st
+                        .tags
+                        .iter()
+                        .map(|tag| tag.name())
+                        .collect::<Vec<_>>()),
+                    vec!["1", "2"]
+                );
+            });
+
+            // Correct usage
+            run_lua! { |Pinnacle|
+                Pinnacle.window.get_all()[1]:move_to_tag(Pinnacle.tag.get("3"))
+            }
+
+            sleep_secs(1);
+
+            assert(&sender, |state| {
+                assert_eq!(
+                    state.windows[0].with_state(|st| st
+                        .tags
+                        .iter()
+                        .map(|tag| tag.name())
+                        .collect::<Vec<_>>()),
+                    vec!["3"]
+                );
+            });
+
+            // Move to the same tag
+            run_lua! { |Pinnacle|
+                Pinnacle.window.get_all()[1]:move_to_tag(Pinnacle.tag.get("3"))
+            }
+
+            sleep_secs(1);
+
+            assert(&sender, |state| {
+                assert_eq!(
+                    state.windows[0].with_state(|st| st
+                        .tags
+                        .iter()
+                        .map(|tag| tag.name())
+                        .collect::<Vec<_>>()),
+                    vec!["3"]
+                );
+            });
+        })
+    }
+}
+
 #[tokio::main]
 #[test]
 async fn window_count_with_tag_is_correct() -> anyhow::Result<()> {
     test_lua_api(|sender| {
         run_lua! { |Pinnacle|
-            Pinnacle.tag.add(Pinnacle.output.get_all()[1], "1")
+            Pinnacle.tag.add(Pinnacle.output.get_focused(), "1")
             Pinnacle.process.spawn("foot")
         }
 
@@ -104,10 +394,107 @@ async fn window_count_with_tag_is_correct() -> anyhow::Result<()> {
 
         assert(&sender, |state| assert_eq!(state.windows.len(), 1));
 
+        run_lua! { |Pinnacle|
+            for i = 1, 20 do
+                Pinnacle.process.spawn("foot")
+            end
+        }
+
         sleep_secs(1);
 
-        run_lua! { |Pinnacle|
-            Pinnacle.quit()
-        }
+        assert(&sender, |state| assert_eq!(state.windows.len(), 21));
+    })
+}
+
+#[tokio::main]
+#[test]
+async fn window_count_without_tag_is_correct() -> anyhow::Result<()> {
+    test_lua_api(|sender| {
+        run_lua! { |Pinnacle|
+            Pinnacle.process.spawn("foot")
+        }
+
+        sleep_secs(1);
+
+        assert(&sender, |state| assert_eq!(state.windows.len(), 1));
+    })
+}
+
+#[tokio::main]
+#[test]
+async fn spawned_window_on_active_tag_has_keyboard_focus() -> anyhow::Result<()> {
+    test_lua_api(|sender| {
+        run_lua! { |Pinnacle|
+            Pinnacle.tag.add(Pinnacle.output.get_focused(), "1")[1]:set_active(true)
+            Pinnacle.process.spawn("foot")
+        }
+
+        sleep_secs(1);
+
+        assert(&sender, |state| {
+            assert_eq!(
+                state
+                    .focused_window(state.focused_output().unwrap())
+                    .unwrap()
+                    .class(),
+                Some("foot".to_string())
+            );
+        });
+    })
+}
+
+#[tokio::main]
+#[test]
+async fn spawned_window_on_inactive_tag_does_not_have_keyboard_focus() -> anyhow::Result<()> {
+    test_lua_api(|sender| {
+        run_lua! { |Pinnacle|
+            Pinnacle.tag.add(Pinnacle.output.get_focused(), "1")
+            Pinnacle.process.spawn("foot")
+        }
+
+        sleep_secs(1);
+
+        assert(&sender, |state| {
+            assert_eq!(state.focused_window(state.focused_output().unwrap()), None);
+        });
+    })
+}
+
+#[tokio::main]
+#[test]
+async fn spawned_window_has_correct_tags() -> anyhow::Result<()> {
+    test_lua_api(|sender| {
+        run_lua! { |Pinnacle|
+            Pinnacle.tag.add(Pinnacle.output.get_focused(), "1", "2", "3")
+            Pinnacle.process.spawn("foot")
+        }
+
+        sleep_secs(1);
+
+        assert(&sender, |state| {
+            assert_eq!(state.windows.len(), 1);
+            assert_eq!(state.windows[0].with_state(|st| st.tags.len()), 1);
+        });
+
+        run_lua! { |Pinnacle|
+            Pinnacle.tag.get("1"):set_active(true)
+            Pinnacle.tag.get("3"):set_active(true)
+            Pinnacle.process.spawn("foot")
+        }
+
+        sleep_secs(1);
+
+        assert(&sender, |state| {
+            assert_eq!(state.windows.len(), 2);
+            assert_eq!(state.windows[1].with_state(|st| st.tags.len()), 2);
+            assert_eq!(
+                state.windows[1].with_state(|st| st
+                    .tags
+                    .iter()
+                    .map(|tag| tag.name())
+                    .collect::<Vec<_>>()),
+                vec!["1", "3"]
+            );
+        });
     })
 }