diff --git a/.gitignore b/.gitignore
index e4e7a1be8..381556a5f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,6 +3,5 @@
 **/*.rs.bk
 Cargo.lock
 bench/target
-tests/png
-tests/pdf
+tests/out
 _things
diff --git a/Cargo.toml b/Cargo.toml
index a32cc8ead..258afd0b1 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -8,26 +8,22 @@ edition = "2018"
 members = ["bench"]
 
 [features]
-default = ["fs", "anyhow"]
+default = ["cli", "fs"]
+cli = ["fs", "anyhow"]
 fs = ["fontdock/fs"]
 
 [dependencies]
-fontdock = { path = "../fontdock", default-features = false }
-pdf-writer = { path = "../pdf-writer" }
 deflate = { version = "0.8.6" }
+fontdock = { path = "../fontdock", default-features = false }
 image = { version = "0.23", default-features = false, features = ["jpeg", "png"] }
 itoa = "0.4"
+pdf-writer = { path = "../pdf-writer" }
 ttf-parser = "0.8.2"
 unicode-xid = "0.2"
-
-# feature = "serde"
+anyhow = { version = "1", optional = true }
 serde = { version = "1", features = ["derive"], optional = true }
 
-# for the CLI
-anyhow = { version = "1", optional = true }
-
 [dev-dependencies]
-memmap = "0.7"
 tiny-skia = "0.2"
 
 [profile.dev]
@@ -38,7 +34,7 @@ lto = true
 
 [[bin]]
 name = "typst"
-required-features = ["fs", "anyhow"]
+required-features = ["cli"]
 
 [[test]]
 name = "typeset"
diff --git a/bench/src/bench.rs b/bench/src/bench.rs
index c232d4bfa..947a02c52 100644
--- a/bench/src/bench.rs
+++ b/bench/src/bench.rs
@@ -13,7 +13,7 @@ use typst::parse::parse;
 use typst::typeset;
 
 const FONT_DIR: &str = "../fonts";
-const COMA: &str = include_str!("../../tests/typ/coma.typ");
+const COMA: &str = include_str!("../../tests/typ/example-coma.typ");
 
 fn benchmarks(c: &mut Criterion) {
     macro_rules! bench {
diff --git a/src/geom/point.rs b/src/geom/point.rs
index 10ab2d3aa..4523a861a 100644
--- a/src/geom/point.rs
+++ b/src/geom/point.rs
@@ -17,6 +17,11 @@ impl Point {
     pub fn new(x: Length, y: Length) -> Self {
         Self { x, y }
     }
+
+    /// Create an instance with two equal components.
+    pub fn uniform(value: Length) -> Self {
+        Self { x: value, y: value }
+    }
 }
 
 impl Get<SpecAxis> for Point {
diff --git a/src/geom/size.rs b/src/geom/size.rs
index 0ad0e0f89..289846591 100644
--- a/src/geom/size.rs
+++ b/src/geom/size.rs
@@ -21,6 +21,11 @@ impl Size {
         Self { width, height }
     }
 
+    /// Create an instance with two equal components.
+    pub fn uniform(value: Length) -> Self {
+        Self { width: value, height: value }
+    }
+
     /// Whether the other size fits into this one (smaller width and height).
     pub fn fits(self, other: Self) -> bool {
         self.width >= other.width && self.height >= other.height
diff --git a/src/main.rs b/src/main.rs
index 3f12655bb..acd2d0cd1 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -59,10 +59,10 @@ fn main() -> anyhow::Result<()> {
         let map = LineMap::new(&src);
         for diag in diags {
             let span = diag.span;
-            let start = map.location(span.start);
-            let end = map.location(span.end);
+            let start = map.location(span.start).unwrap();
+            let end = map.location(span.end).unwrap();
             println!(
-                "  {}: {}:{}-{}: {}",
+                "{}: {}:{}-{}: {}",
                 diag.v.level,
                 src_path.display(),
                 start,
diff --git a/src/parse/lines.rs b/src/parse/lines.rs
index ce5a1fe5a..be120d8aa 100644
--- a/src/parse/lines.rs
+++ b/src/parse/lines.rs
@@ -1,7 +1,7 @@
 //! Conversion of byte positions to line/column locations.
 
 use super::Scanner;
-use crate::syntax::{Location, Pos};
+use crate::syntax::{Location, Offset, Pos};
 
 /// Enables conversion of byte position to locations.
 pub struct LineMap<'s> {
@@ -25,23 +25,48 @@ impl<'s> LineMap<'s> {
     }
 
     /// Convert a byte position to a location.
-    ///
-    /// # Panics
-    /// This panics if the position is out of bounds.
-    pub fn location(&self, pos: Pos) -> Location {
+    pub fn location(&self, pos: Pos) -> Option<Location> {
+        // Find the line which contains the position.
         let line_index = match self.line_starts.binary_search(&pos) {
             Ok(i) => i,
             Err(i) => i - 1,
         };
 
-        let line_start = self.line_starts[line_index];
-        let head = &self.src[line_start.to_usize() .. pos.to_usize()];
+        let start = self.line_starts.get(line_index)?;
+        let head = self.src.get(start.to_usize() .. pos.to_usize())?;
         let column_index = head.chars().count();
 
-        Location {
+        Some(Location {
             line: 1 + line_index as u32,
             column: 1 + column_index as u32,
-        }
+        })
+    }
+
+    /// Convert a location to a byte position.
+    pub fn pos(&self, location: Location) -> Option<Pos> {
+        // Determine the boundaries of the line.
+        let line_idx = location.line.checked_sub(1)? as usize;
+        let line_start = self.line_starts.get(line_idx)?;
+        let line_end = self
+            .line_starts
+            .get(location.line as usize)
+            .map_or(self.src.len(), |pos| pos.to_usize());
+
+        let line = self.src.get(line_start.to_usize() .. line_end)?;
+
+        // Find the index in the line. For the first column, the index is always zero. For
+        // other columns, we have to look at which byte the char directly before the
+        // column in question ends. We can't do `nth(column_idx)` directly since the
+        // column may be behind the last char.
+        let column_idx = location.column.checked_sub(1)? as usize;
+        let line_offset = if let Some(prev_idx) = column_idx.checked_sub(1) {
+            let (idx, prev) = line.char_indices().nth(prev_idx)?;
+            idx + prev.len_utf8()
+        } else {
+            0
+        };
+
+        Some(line_start.offset(Pos(line_offset as u32)))
     }
 }
 
@@ -71,18 +96,26 @@ mod tests {
     #[test]
     fn test_line_map_location() {
         let map = LineMap::new(TEST);
-        assert_eq!(map.location(Pos(0)), Location::new(1, 1));
-        assert_eq!(map.location(Pos(2)), Location::new(1, 2));
-        assert_eq!(map.location(Pos(6)), Location::new(1, 6));
-        assert_eq!(map.location(Pos(7)), Location::new(2, 1));
-        assert_eq!(map.location(Pos(8)), Location::new(2, 2));
-        assert_eq!(map.location(Pos(12)), Location::new(2, 3));
-        assert_eq!(map.location(Pos(21)), Location::new(4, 4));
+        assert_eq!(map.location(Pos(0)), Some(Location::new(1, 1)));
+        assert_eq!(map.location(Pos(2)), Some(Location::new(1, 2)));
+        assert_eq!(map.location(Pos(6)), Some(Location::new(1, 6)));
+        assert_eq!(map.location(Pos(7)), Some(Location::new(2, 1)));
+        assert_eq!(map.location(Pos(8)), Some(Location::new(2, 2)));
+        assert_eq!(map.location(Pos(12)), Some(Location::new(2, 3)));
+        assert_eq!(map.location(Pos(21)), Some(Location::new(4, 4)));
+        assert_eq!(map.location(Pos(22)), None);
     }
 
     #[test]
-    #[should_panic]
-    fn test_line_map_panics_out_of_bounds() {
-        LineMap::new(TEST).location(Pos(22));
+    fn test_line_map_pos() {
+        fn assert_round_trip(map: &LineMap, pos: Pos) {
+            assert_eq!(map.location(pos).and_then(|loc| map.pos(loc)), Some(pos));
+        }
+
+        let map = LineMap::new(TEST);
+        assert_round_trip(&map, Pos(0));
+        assert_round_trip(&map, Pos(7));
+        assert_round_trip(&map, Pos(12));
+        assert_round_trip(&map, Pos(21));
     }
 }
diff --git a/src/parse/tests.rs b/src/parse/tests.rs
index 054b2cd90..172b1d15a 100644
--- a/src/parse/tests.rs
+++ b/src/parse/tests.rs
@@ -56,24 +56,31 @@ use Unit::*;
 fn Id(ident: &str) -> Expr {
     Expr::Lit(Lit::Ident(Ident(ident.to_string())))
 }
+
 fn Bool(b: bool) -> Expr {
     Expr::Lit(Lit::Bool(b))
 }
+
 fn Int(int: i64) -> Expr {
     Expr::Lit(Lit::Int(int))
 }
+
 fn Float(float: f64) -> Expr {
     Expr::Lit(Lit::Float(float))
 }
+
 fn Percent(percent: f64) -> Expr {
     Expr::Lit(Lit::Percent(percent))
 }
+
 fn Length(val: f64, unit: Unit) -> Expr {
     Expr::Lit(Lit::Length(val, unit))
 }
+
 fn Color(color: RgbaColor) -> Expr {
     Expr::Lit(Lit::Color(color))
 }
+
 fn Str(string: &str) -> Expr {
     Expr::Lit(Lit::Str(string.to_string()))
 }
@@ -98,6 +105,7 @@ fn Unary(op: impl Into<Spanned<UnOp>>, expr: impl Into<Spanned<Expr>>) -> Expr {
         expr: expr.into().map(Box::new),
     })
 }
+
 fn Binary(
     op: impl Into<Spanned<BinOp>>,
     lhs: impl Into<Spanned<Expr>>,
diff --git a/tests/README.md b/tests/README.md
index 89c31c890..7d9c3edac 100644
--- a/tests/README.md
+++ b/tests/README.md
@@ -1,8 +1,7 @@
 # Tests
 
 - `typ`: Input files
-- `pdf`: PDF files produced by tests
-- `png`: PNG files produced by tests
-- `cmp`: Reference images which the PNGs are compared to byte-wise to determine
-         whether the test passed or failed
+- `ref`: Reference images which the output is compared with to determine
+         whether a test passed or failed
 - `res`: Resource files used by tests
+- `out`: PNG and PDF files produced by tests
diff --git a/tests/cmp/coma.png b/tests/cmp/coma.png
deleted file mode 100644
index d0c524ecf..000000000
Binary files a/tests/cmp/coma.png and /dev/null differ
diff --git a/tests/cmp/image.png b/tests/cmp/image.png
deleted file mode 100644
index 5bf744e99..000000000
Binary files a/tests/cmp/image.png and /dev/null differ
diff --git a/tests/ref/empty.png b/tests/ref/empty.png
new file mode 100644
index 000000000..812a3758c
Binary files /dev/null and b/tests/ref/empty.png differ
diff --git a/tests/ref/example-coma.png b/tests/ref/example-coma.png
new file mode 100644
index 000000000..0c18b810c
Binary files /dev/null and b/tests/ref/example-coma.png differ
diff --git a/tests/ref/image-error.png b/tests/ref/image-error.png
new file mode 100644
index 000000000..812a3758c
Binary files /dev/null and b/tests/ref/image-error.png differ
diff --git a/tests/ref/image-fit.png b/tests/ref/image-fit.png
new file mode 100644
index 000000000..b89e78fd1
Binary files /dev/null and b/tests/ref/image-fit.png differ
diff --git a/tests/ref/image-jpeg.png b/tests/ref/image-jpeg.png
new file mode 100644
index 000000000..ef9e74cbd
Binary files /dev/null and b/tests/ref/image-jpeg.png differ
diff --git a/tests/ref/image-png.png b/tests/ref/image-png.png
new file mode 100644
index 000000000..4e0818d21
Binary files /dev/null and b/tests/ref/image-png.png differ
diff --git a/tests/typ/empty.typ b/tests/typ/empty.typ
new file mode 100644
index 000000000..e69de29bb
diff --git a/tests/typ/coma.typ b/tests/typ/example-coma.typ
similarity index 91%
rename from tests/typ/coma.typ
rename to tests/typ/example-coma.typ
index 839335b70..f841a1221 100644
--- a/tests/typ/coma.typ
+++ b/tests/typ/example-coma.typ
@@ -1,3 +1,5 @@
+// Small integration test of syntax, page setup, box layout and alignment.
+
 [page: width=450pt, height=300pt, margins=1cm]
 
 [box][
diff --git a/tests/typ/image-error.typ b/tests/typ/image-error.typ
new file mode 100644
index 000000000..4fde4ab29
--- /dev/null
+++ b/tests/typ/image-error.typ
@@ -0,0 +1,8 @@
+// error: 5:9-5:30 failed to load image
+// error: 8:9-8:30 failed to load image
+
+// File does not exist.
+[image: "path/does/not/exist"]
+
+// File exists, but is no image.
+[image: "typ/image-error.typ"]
diff --git a/tests/typ/image-fit.typ b/tests/typ/image-fit.typ
new file mode 100644
index 000000000..b735f058e
--- /dev/null
+++ b/tests/typ/image-fit.typ
@@ -0,0 +1,21 @@
+// Fit to width of page.
+[image: "res/rhino.png"]
+
+// Fit to height of page.
+[page: width=270pt][
+    [image: "res/rhino.png"]
+]
+
+// Set width explicitly.
+[image: "res/rhino.png", width=50pt]
+
+// Set height explicitly.
+[image: "res/rhino.png", height=50pt]
+
+// Set width and height explicitly and force stretching.
+[image: "res/rhino.png", width=25pt, height=50pt]
+
+// Make sure the bounding-box of the image is correct.
+[align: bottom, right][
+    [image: "res/tiger.jpg"]
+]
diff --git a/tests/typ/image-jpeg.typ b/tests/typ/image-jpeg.typ
new file mode 100644
index 000000000..48cf1a0dc
--- /dev/null
+++ b/tests/typ/image-jpeg.typ
@@ -0,0 +1,2 @@
+// Load an RGB JPEG image.
+[image: "res/tiger.jpg"]
diff --git a/tests/typ/image-png.typ b/tests/typ/image-png.typ
new file mode 100644
index 000000000..482591e92
--- /dev/null
+++ b/tests/typ/image-png.typ
@@ -0,0 +1,2 @@
+// Load an RGBA PNG image.
+[image: "res/rhino.png"]
diff --git a/tests/typ/image.typ b/tests/typ/image.typ
deleted file mode 100644
index 6ae349a10..000000000
--- a/tests/typ/image.typ
+++ /dev/null
@@ -1,15 +0,0 @@
-[page: width=5cm, height=5cm, margins=0.25cm]
-
-[image: "res/tiger.jpg"]
-
-[pagebreak]
-
-# Tiger
-[image: "res/tiger.jpg", width=2cm]
-[image: "res/rhino.png", width=1cm]
-[image: "res/rhino.png", height=2cm]
-
-[pagebreak]
-
-[align: center, bottom]
-[image: "res/tiger.jpg", width=2cm, height=3.5cm]
diff --git a/tests/typeset.rs b/tests/typeset.rs
index 807215ed1..037bd7efa 100644
--- a/tests/typeset.rs
+++ b/tests/typeset.rs
@@ -1,35 +1,35 @@
 use std::cell::RefCell;
 use std::env;
 use std::ffi::OsStr;
-use std::fs::{self, File};
+use std::fs;
 use std::path::Path;
 use std::rc::Rc;
 
 use fontdock::fs::{FsIndex, FsSource};
 use image::{GenericImageView, Rgba};
-use memmap::Mmap;
 use tiny_skia::{
     Canvas, Color, ColorU8, FillRule, FilterQuality, Paint, PathBuilder, Pattern, Pixmap,
     Rect, SpreadMode, Transform,
 };
 use ttf_parser::OutlineBuilder;
 
-use typst::diag::{Feedback, Pass};
+use typst::diag::{Diag, Feedback, Level, Pass};
 use typst::env::{Env, ImageResource, ResourceLoader, SharedEnv};
 use typst::eval::State;
 use typst::export::pdf;
 use typst::font::FontLoader;
-use typst::geom::{Length, Point};
+use typst::geom::{Length, Point, Sides, Size};
 use typst::layout::{BoxLayout, ImageElement, LayoutElement};
-use typst::parse::LineMap;
+use typst::parse::{LineMap, Scanner};
 use typst::shaping::Shaped;
+use typst::syntax::{Location, Pos, SpanVec, SpanWith, Spanned};
 use typst::typeset;
 
-const FONT_DIR: &str = "../fonts";
 const TYP_DIR: &str = "typ";
-const PDF_DIR: &str = "pdf";
-const PNG_DIR: &str = "png";
-const CMP_DIR: &str = "cmp";
+const REF_DIR: &str = "ref";
+const PNG_DIR: &str = "out/png";
+const PDF_DIR: &str = "out/pdf";
+const FONT_DIR: &str = "../fonts";
 
 fn main() {
     env::set_current_dir(env::current_dir().unwrap().join("tests")).unwrap();
@@ -44,12 +44,8 @@ fn main() {
         }
 
         let name = src_path.file_stem().unwrap().to_string_lossy().to_string();
-        let pdf_path = Path::new(PDF_DIR).join(&name).with_extension("pdf");
-        let png_path = Path::new(PNG_DIR).join(&name).with_extension("png");
-        let ref_path = Path::new(CMP_DIR).join(&name).with_extension("png");
-
         if filter.matches(&name) {
-            filtered.push((name, src_path, pdf_path, png_path, ref_path));
+            filtered.push((name, src_path));
         }
     }
 
@@ -62,8 +58,8 @@ fn main() {
         println!("Running {} tests", len);
     }
 
-    fs::create_dir_all(PDF_DIR).unwrap();
     fs::create_dir_all(PNG_DIR).unwrap();
+    fs::create_dir_all(PDF_DIR).unwrap();
 
     let mut index = FsIndex::new();
     index.search_dir(FONT_DIR);
@@ -76,29 +72,12 @@ fn main() {
 
     let mut ok = true;
 
-    for (name, src_path, pdf_path, png_path, ref_path) in filtered {
-        print!("Testing {}.", name);
-        test(&src_path, &pdf_path, &png_path, &env);
+    for (name, src_path) in filtered {
+        let png_path = Path::new(PNG_DIR).join(&name).with_extension("png");
+        let pdf_path = Path::new(PDF_DIR).join(&name).with_extension("pdf");
+        let ref_path = Path::new(REF_DIR).join(&name).with_extension("png");
 
-        let png_file = File::open(&png_path).unwrap();
-        let ref_file = match File::open(&ref_path) {
-            Ok(file) => file,
-            Err(_) => {
-                println!(" Failed to open reference image. ❌");
-                ok = false;
-                continue;
-            }
-        };
-
-        let a = unsafe { Mmap::map(&png_file).unwrap() };
-        let b = unsafe { Mmap::map(&ref_file).unwrap() };
-
-        if *a != *b {
-            println!(" Does not match reference image. ❌");
-            ok = false;
-        } else {
-            println!(" Okay. ✔");
-        }
+        ok &= test(&name, &src_path, &pdf_path, &png_path, &ref_path, &env);
     }
 
     if !ok {
@@ -106,41 +85,6 @@ fn main() {
     }
 }
 
-fn test(src_path: &Path, pdf_path: &Path, png_path: &Path, env: &SharedEnv) {
-    let src = fs::read_to_string(src_path).unwrap();
-    let state = State::default();
-    let Pass {
-        output: layouts,
-        feedback: Feedback { mut diags, .. },
-    } = typeset(&src, Rc::clone(env), state);
-
-    if !diags.is_empty() {
-        diags.sort();
-
-        let map = LineMap::new(&src);
-        for diag in diags {
-            let span = diag.span;
-            let start = map.location(span.start);
-            let end = map.location(span.end);
-            println!(
-                "  {}: {}:{}-{}: {}",
-                diag.v.level,
-                src_path.display(),
-                start,
-                end,
-                diag.v.message,
-            );
-        }
-    }
-
-    let env = env.borrow();
-    let canvas = draw(&layouts, &env, 2.0);
-    canvas.pixmap.save_png(png_path).unwrap();
-
-    let pdf_data = pdf::export(&layouts, &env);
-    fs::write(pdf_path, pdf_data).unwrap();
-}
-
 struct TestFilter {
     filter: Vec<String>,
     perfect: bool,
@@ -171,6 +115,111 @@ impl TestFilter {
     }
 }
 
+fn test(
+    name: &str,
+    src_path: &Path,
+    pdf_path: &Path,
+    png_path: &Path,
+    ref_path: &Path,
+    env: &SharedEnv,
+) -> bool {
+    println!("Testing {}.", name);
+
+    let src = fs::read_to_string(src_path).unwrap();
+    let map = LineMap::new(&src);
+    let ref_diags = parse_diags(&src, &map);
+
+    let mut state = State::default();
+    state.page.size = Size::uniform(Length::pt(120.0));
+    state.page.margins = Sides::uniform(Some(Length::pt(10.0).into()));
+
+    let Pass {
+        output: layouts,
+        feedback: Feedback { mut diags, .. },
+    } = typeset(&src, Rc::clone(env), state);
+    diags.sort();
+
+    let env = env.borrow();
+    let canvas = draw(&layouts, &env, 2.0);
+    canvas.pixmap.save_png(png_path).unwrap();
+
+    let pdf_data = pdf::export(&layouts, &env);
+    fs::write(pdf_path, pdf_data).unwrap();
+
+    let mut ok = true;
+
+    if diags != ref_diags {
+        println!("  Does not match expected diagnostics. ❌");
+        ok = false;
+
+        for diag in &diags {
+            if ref_diags.binary_search(diag).is_err() {
+                print!("    Unexpected | ");
+                print_diag(diag, &map);
+            }
+        }
+
+        for diag in &ref_diags {
+            if diags.binary_search(diag).is_err() {
+                print!("    Missing    | ");
+                print_diag(diag, &map);
+            }
+        }
+    }
+
+    if let Ok(ref_pixmap) = Pixmap::load_png(&ref_path) {
+        if canvas.pixmap != ref_pixmap {
+            println!("  Does not match reference image. ❌");
+            ok = false;
+        }
+    } else {
+        println!("  Failed to open reference image. ❌");
+        ok = false;
+    }
+
+    if ok {
+        println!("\x1b[1ATesting {}. ✔", name);
+    }
+
+    ok
+}
+
+fn parse_diags(src: &str, map: &LineMap) -> SpanVec<Diag> {
+    let mut diags = vec![];
+
+    for line in src.lines() {
+        let (level, rest) = if let Some(rest) = line.strip_prefix("// error: ") {
+            (Level::Error, rest)
+        } else if let Some(rest) = line.strip_prefix("// warning: ") {
+            (Level::Warning, rest)
+        } else {
+            continue;
+        };
+
+        fn pos(s: &mut Scanner, map: &LineMap) -> Pos {
+            let (line, _, column) = (num(s), s.eat_assert(':'), num(s));
+            map.pos(Location { line, column }).unwrap()
+        }
+
+        fn num(s: &mut Scanner) -> u32 {
+            s.eat_while(|c| c.is_numeric()).parse().unwrap()
+        }
+
+        let mut s = Scanner::new(rest);
+        let (start, _, end) = (pos(&mut s, map), s.eat_assert('-'), pos(&mut s, map));
+        diags.push(Diag::new(level, s.rest().trim()).span_with(start .. end));
+    }
+
+    diags.sort();
+    diags
+}
+
+fn print_diag(diag: &Spanned<Diag>, map: &LineMap) {
+    let start = map.location(diag.span.start).unwrap();
+    let end = map.location(diag.span.end).unwrap();
+    println!("{}: {}-{}: {}", diag.v.level, start, end, diag.v.message,);
+}
+
 fn draw(layouts: &[BoxLayout], env: &Env, pixel_per_pt: f32) -> Canvas {
     let pad = Length::pt(5.0);