Assertions with [eq] + better tests 🩺

31 files changed, 284 insertions, 135 deletions

diff --git a/src/eval/call.rs b/src/eval/call.rs
index 8e75f17c..5b0628a8 100644
--- a/src/eval/call.rs
+++ b/src/eval/call.rs
@@ -73,7 +73,7 @@ impl Args {
     where
         T: Cast<Spanned<Value>>,
     {
-        self.pos.iter_mut().find_map(move |slot| try_cast(ctx, slot))
+        (0 .. self.pos.len()).find_map(move |i| try_cast(ctx, &mut self.pos, i))
     }
 
     /// Find and remove the first convertible positional argument, producing an
@@ -97,7 +97,16 @@ impl Args {
     where
         T: Cast<Spanned<Value>>,
     {
-        self.pos.iter_mut().filter_map(move |slot| try_cast(ctx, slot))
+        let mut i = 0;
+        std::iter::from_fn(move || {
+            while i < self.pos.len() {
+                if let Some(val) = try_cast(ctx, &mut self.pos, i) {
+                    return Some(val);
+                }
+                i += 1;
+            }
+            None
+        })
     }
 
     /// Convert and remove the value for the given named argument, producing an
@@ -163,17 +172,26 @@ where
 
 /// Try to cast the value in the slot into `T`, putting it back if the
 /// conversion fails.
-fn try_cast<T>(ctx: &mut EvalContext, slot: &mut Spanned<Value>) -> Option<T>
+fn try_cast<T>(
+    ctx: &mut EvalContext,
+    vec: &mut Vec<Spanned<Value>>,
+    i: usize,
+) -> Option<T>
 where
     T: Cast<Spanned<Value>>,
 {
     // Replace with error placeholder when conversion works since error values
     // are ignored when generating "unexpected argument" errors.
-    let value = std::mem::replace(slot, Spanned::zero(Value::Error));
+    let slot = &mut vec[i];
+    let value = std::mem::replace(slot, Spanned::zero(Value::None));
     let span = value.span;
     match T::cast(value) {
-        CastResult::Ok(t) => Some(t),
+        CastResult::Ok(t) => {
+            vec.remove(i);
+            Some(t)
+        }
         CastResult::Warn(t, m) => {
+            vec.remove(i);
             ctx.diag(warning!(span, "{}", m));
             Some(t)
         }
diff --git a/src/parse/mod.rs b/src/parse/mod.rs
index b6836d38..7c92185d 100644
--- a/src/parse/mod.rs
+++ b/src/parse/mod.rs
@@ -117,7 +117,7 @@ fn heading(p: &mut Parser) -> NodeHeading {
 
     // Parse the heading contents.
     let mut contents = vec![];
-    while p.check(|t| !matches!(t, Token::Space(n) if n > 0)) {
+    while p.check(|t| !matches!(t, Token::Space(n) if n >= 1)) {
         if let Some(node) = p.span_if(|p| node(p, &mut false)) {
             contents.push(node);
         }
@@ -388,8 +388,8 @@ fn string(p: &mut Parser, token: TokenStr) -> String {
 /// Parse a let expresion.
 fn expr_let(p: &mut Parser) -> Option<Expr> {
     p.push_mode(TokenMode::Code);
-    p.start_group(Group::Terminated);
     p.eat_assert(Token::Let);
+    p.start_group(Group::Expr);
 
     let pat = p.span_if(ident);
     let mut rhs = None;
@@ -404,11 +404,11 @@ fn expr_let(p: &mut Parser) -> Option<Expr> {
         p.diag_expected("identifier");
     }
 
-    while !p.eof() {
-        p.diag_unexpected();
+    p.pop_mode();
+    if !p.eof() {
+        p.diag_expected("semicolon or line break");
     }
 
-    p.pop_mode();
     p.end_group();
     pat.map(|pat| Expr::Let(ExprLet { pat, expr: rhs }))
 }
diff --git a/src/parse/parser.rs b/src/parse/parser.rs
index 2b5fe720..8c27c8f7 100644
--- a/src/parse/parser.rs
+++ b/src/parse/parser.rs
@@ -112,16 +112,14 @@ impl<'s> Parser<'s> {
     /// # Panics
     /// This panics if the next token does not start the given group.
     pub fn start_group(&mut self, group: Group) {
+        self.groups.push(group);
         match group {
             Group::Paren => self.eat_assert(Token::LeftParen),
             Group::Bracket => self.eat_assert(Token::LeftBracket),
             Group::Brace => self.eat_assert(Token::LeftBrace),
-            Group::Subheader => {}
-            Group::Terminated => {}
+            Group::Expr => self.repeek(),
+            Group::Subheader => self.repeek(),
         }
-
-        self.groups.push(group);
-        self.repeek();
     }
 
     /// Ends the parsing of a group and returns the span of the whole group.
@@ -129,26 +127,21 @@ impl<'s> Parser<'s> {
     /// # Panics
     /// This panics if no group was started.
     pub fn end_group(&mut self) {
-        // Check that we are indeed at the end of the group.
-        debug_assert_eq!(self.peek(), None, "unfinished group");
-
         let group = self.groups.pop().expect("no started group");
         self.repeek();
 
-        let end = match group {
-            Group::Paren => Some(Token::RightParen),
-            Group::Bracket => Some(Token::RightBracket),
-            Group::Brace => Some(Token::RightBrace),
-            Group::Subheader => None,
-            Group::Terminated => Some(Token::Semicolon),
+        let (end, required) = match group {
+            Group::Paren => (Token::RightParen, true),
+            Group::Bracket => (Token::RightBracket, true),
+            Group::Brace => (Token::RightBrace, true),
+            Group::Expr => (Token::Semicolon, false),
+            Group::Subheader => return,
         };
 
-        if let Some(token) = end {
-            if self.next == Some(token) {
-                self.bump();
-            } else {
-                self.diag(error!(self.next_start, "expected {}", token.name()));
-            }
+        if self.next == Some(end) {
+            self.bump();
+        } else if required {
+            self.diag(error!(self.next_start, "expected {}", end.name()));
         }
     }
 
@@ -169,7 +162,7 @@ impl<'s> Parser<'s> {
     where
         F: FnOnce(&mut Self) -> Option<T>,
     {
-        self.span(|p| f(p)).transpose()
+        self.span(f).transpose()
     }
 
     /// Consume the next token.
@@ -269,17 +262,21 @@ impl<'s> Parser<'s> {
 
         match self.tokens.mode() {
             TokenMode::Markup => {}
-            TokenMode::Code => {
-                while matches!(
-                    self.next,
-                    Some(Token::Space(_)) |
-                    Some(Token::LineComment(_)) |
-                    Some(Token::BlockComment(_))
-                ) {
-                    self.next_start = self.tokens.pos();
-                    self.next = self.tokens.next();
+            TokenMode::Code => loop {
+                match self.next {
+                    Some(Token::Space(n)) => {
+                        if n >= 1 && self.groups.last() == Some(&Group::Expr) {
+                            break;
+                        }
+                    }
+                    Some(Token::LineComment(_)) => {}
+                    Some(Token::BlockComment(_)) => {}
+                    _ => break,
                 }
-            }
+
+                self.next_start = self.tokens.pos();
+                self.next = self.tokens.next();
+            },
         }
 
         self.repeek();
@@ -287,16 +284,22 @@ impl<'s> Parser<'s> {
 
     fn repeek(&mut self) {
         self.peeked = self.next;
-        if self.groups.contains(&match self.next {
-            Some(Token::RightParen) => Group::Paren,
-            Some(Token::RightBracket) => Group::Bracket,
-            Some(Token::RightBrace) => Group::Brace,
-            Some(Token::Pipe) => Group::Subheader,
-            Some(Token::Semicolon) => Group::Terminated,
+        let token = match self.next {
+            Some(token) => token,
+            None => return,
+        };
+
+        match token {
+            Token::RightParen if self.groups.contains(&Group::Paren) => {}
+            Token::RightBracket if self.groups.contains(&Group::Bracket) => {}
+            Token::RightBrace if self.groups.contains(&Group::Brace) => {}
+            Token::Semicolon if self.groups.contains(&Group::Expr) => {}
+            Token::Space(n) if n >= 1 && self.groups.last() == Some(&Group::Expr) => {}
+            Token::Pipe if self.groups.contains(&Group::Subheader) => {}
             _ => return,
-        }) {
-            self.peeked = None;
         }
+
+        self.peeked = None;
     }
 }
 
@@ -316,9 +319,9 @@ pub enum Group {
     Bracket,
     /// A curly-braced group: `{...}`.
     Brace,
+    /// A group ended by a semicolon or a line break: `;`, `\n`.
+    Expr,
     /// A group ended by a chained subheader or a closing bracket:
     /// `... >>`, `...]`.
     Subheader,
-    /// A group ended by a semicolon: `;`.
-    Terminated,
 }
diff --git a/tests/lang/ref/arrays.png b/tests/lang/ref/arrays.png
index 2d70a3f6..36845b5f 100644
--- a/tests/lang/ref/arrays.png
+++ b/tests/lang/ref/arrays.png
diff --git a/tests/lang/ref/basics.png b/tests/lang/ref/basics.png
deleted file mode 100644
index 3c3dd7a0..00000000
--- a/tests/lang/ref/basics.png
+++ /dev/null
diff --git a/tests/lang/ref/blocks.png b/tests/lang/ref/blocks.png
index ca826c1b..22a5722a 100644
--- a/tests/lang/ref/blocks.png
+++ b/tests/lang/ref/blocks.png
diff --git a/tests/lang/ref/emph-strong.png b/tests/lang/ref/emph-strong.png
new file mode 100644
index 00000000..36392f8c
--- /dev/null
+++ b/tests/lang/ref/emph-strong.png
diff --git a/tests/lang/ref/expressions.png b/tests/lang/ref/expressions.png
deleted file mode 100644
index 309c32f1..00000000
--- a/tests/lang/ref/expressions.png
+++ /dev/null
diff --git a/tests/lang/ref/headings.png b/tests/lang/ref/headings.png
index 1f374cce..c8d83165 100644
--- a/tests/lang/ref/headings.png
+++ b/tests/lang/ref/headings.png
diff --git a/tests/lang/ref/let.png b/tests/lang/ref/let.png
index be9d8397..d9833391 100644
--- a/tests/lang/ref/let.png
+++ b/tests/lang/ref/let.png
diff --git a/tests/lang/ref/linebreaks.png b/tests/lang/ref/linebreaks.png
new file mode 100644
index 00000000..5268ed64
--- /dev/null
+++ b/tests/lang/ref/linebreaks.png
diff --git a/tests/lang/ref/nbsp.png b/tests/lang/ref/nbsp.png
new file mode 100644
index 00000000..537a70eb
--- /dev/null
+++ b/tests/lang/ref/nbsp.png
diff --git a/tests/lang/ref/raw.png b/tests/lang/ref/raw.png
index f88194c0..8b68922a 100644
--- a/tests/lang/ref/raw.png
+++ b/tests/lang/ref/raw.png
diff --git a/tests/lang/ref/text.png b/tests/lang/ref/text.png
new file mode 100644
index 00000000..54479229
--- /dev/null
+++ b/tests/lang/ref/text.png
diff --git a/tests/lang/ref/values.png b/tests/lang/ref/values.png
index 762ad64e..d4411cc8 100644
--- a/tests/lang/ref/values.png
+++ b/tests/lang/ref/values.png
diff --git a/tests/lang/typ/arrays.typ b/tests/lang/typ/arrays.typ
index 0b8fb866..3c290e50 100644
--- a/tests/lang/typ/arrays.typ
+++ b/tests/lang/typ/arrays.typ
@@ -1,6 +1,9 @@
 // Empty.
 {()}
 
+// Not an array, just a parenthesized expression.
+{(1)}
+
 // One item and trailing comma.
 {(-1,)}
 
@@ -13,21 +16,31 @@
      , #003
      ,)}
 
+// Missing closing paren.
 // Error: 1:3-1:3 expected closing paren
 {(}
 
-// Error: 2:4-2:6 expected expression, found end of block comment
-// Error: 1:4-1:4 expected comma
+// Not an array.
+// Error: 1:2-1:3 expected expression, found closing paren
+{)}
+
+// Missing comma and bad expression.
+// Error: 2:4-2:4 expected comma
+// Error: 1:4-1:6 expected expression, found end of block comment
 {(1*/2)}
 
+// Bad expression.
 // Error: 1:6-1:8 expected expression, found invalid token
 {(1, 1u 2)}
 
+// Leading comma is not an expression.
 // Error: 1:3-1:4 expected expression, found comma
 {(,1)}
 
+// Missing expression makes named pair incomplete, making this an empty array.
 // Error: 1:5-1:5 expected expression
 {(a:)}
 
+// Named pair after this is already identified as an array.
 // Error: 1:6-1:10 expected expression, found named pair
 {(1, b: 2)}
diff --git a/tests/lang/typ/basics.typ b/tests/lang/typ/basics.typ
deleted file mode 100644
index 9220e376..00000000
--- a/tests/lang/typ/basics.typ
+++ /dev/null
@@ -1,14 +0,0 @@
-Hello 🌏!
-
-_Emph_ and *strong*!
-
-The non-breaking~space does not work.
-
-// Directly after word.
-Line\ Break
-
-// Spaces around.
-Line \ Break
-
-// Directly before word does not work.
-No \Break
diff --git a/tests/lang/typ/blocks.typ b/tests/lang/typ/blocks.typ
index cadd30dd..faef0987 100644
--- a/tests/lang/typ/blocks.typ
+++ b/tests/lang/typ/blocks.typ
@@ -1,21 +1,26 @@
+// Basic expression.
 {1}
 
-// Function calls.
-{f(1)}
-{[[f 1]]}
-
 // Error: 1:2-1:2 expected expression
 {}
 
+// Bad expression.
 // Error: 1:2-1:4 expected expression, found invalid token
 {1u}
 
+// Two expressions are not allowed.
+// Error: 1:4-1:5 unexpected integer
+{2 3}
+
+// Missing closing brace in nested block.
 // Error: 1:5-1:5 expected closing brace
 {({1) + 2}
 
-// Error: 1:12-1:12 expected closing bracket
-{[*] + [ok*}
+// Missing closing bracket in template expression.
+// Error: 1:11-1:11 expected closing bracket
+{[_] + [4_}
 
+// Opening brace is ignored after one expression is parsed.
 // Error: 2:4-2:5 unexpected hex value
 // Error: 1:5-1:6 unexpected opening brace
-{1 #{} _end_
+{5 #{}*.*
diff --git a/tests/lang/typ/comments.typ b/tests/lang/typ/comments.typ
index c5b04967..5118a05e 100644
--- a/tests/lang/typ/comments.typ
+++ b/tests/lang/typ/comments.typ
@@ -1,18 +1,19 @@
-// Test whether line comment acts as spacing.
+// Line comment acts as spacing.
 A// you
 B
 
-// Test whether block comment acts as spacing.
+// Block comment does not act as spacing.
 C/*
  /* */
 */D
 
-// Test in expressions.
+// Works in headers.
 [f /*1*/ a: "b" //
 , 1]
 
+// End should not appear without start.
 // Error: 1:7-1:9 unexpected end of block comment
 /* */ */
 
-// Unterminated block comment is okay.
+// Unterminated is okay.
 /*
diff --git a/tests/lang/typ/dictionaries.typ b/tests/lang/typ/dictionaries.typ
index c729b92c..63d9db9e 100644
--- a/tests/lang/typ/dictionaries.typ
+++ b/tests/lang/typ/dictionaries.typ
@@ -4,9 +4,11 @@
 // Two pairs.
 {(one: 1, two: 2)}
 
+// Simple expression after this is already identified as a dictionary.
 // Error: 1:9-1:10 expected named pair, found expression
 {(a: 1, b)}
 
+// Identified as dictionary by initial colon.
 // Error: 4:4-4:5 expected named pair, found expression
 // Error: 3:5-3:5 expected comma
 // Error: 2:12-2:16 expected identifier
diff --git a/tests/lang/typ/emph-strong.typ b/tests/lang/typ/emph-strong.typ
new file mode 100644
index 00000000..dcd17337
--- /dev/null
+++ b/tests/lang/typ/emph-strong.typ
@@ -0,0 +1,11 @@
+// Basic.
+_Emph_ and *strong*!
+
+// Inside of words.
+Pa_rtl_y emphasized or str*ength*ened.
+
+// Scoped to body.
+[box][*Sco_ped] to body.
+
+// Unterminated is fine.
+_The End
diff --git a/tests/lang/typ/escaping.typ b/tests/lang/typ/escaping.typ
index cb663612..abf124ce 100644
--- a/tests/lang/typ/escaping.typ
+++ b/tests/lang/typ/escaping.typ
@@ -18,8 +18,10 @@
 // Escaped escape sequence.
 \u{41} vs. \\u\{41\}
 
+// Unicode codepoint does not exist.
 // Error: 1:1-1:11 invalid unicode escape sequence
 \u{FFFFFF}
 
+// Unterminated.
 // Error: 1:6-1:6 expected closing brace
 \u{41*Bold*
diff --git a/tests/lang/typ/expressions.typ b/tests/lang/typ/expressions.typ
index 01725289..74150c4b 100644
--- a/tests/lang/typ/expressions.typ
+++ b/tests/lang/typ/expressions.typ
@@ -1,37 +1,43 @@
+// Ref: false
+
 #let a = 2;
 #let b = 4;
 
+// Paren call.
+[eq f(1), "f(1)"]
+[eq type(1), "integer"]
+
 // Unary operations.
-{+1}
-{-1}
-{--1}
+[eq +1, 1]
+[eq -1, 1-2]
+[eq --1, 1]
 
 // Binary operations.
-{"a"+"b"}
-{1-2}
-{a * b}
-{12pt/.4}
+[eq "a" + "b", "ab"]
+[eq 1-4, 3*-1]
+[eq a * b, 8]
+[eq 12pt/.4, 30pt]
 
 // Associativity.
-{1+2+3}
-{1/2*3}
+[eq 1+2+3, 6]
+[eq 1/2*3, 1.5]
 
 // Precedence.
-{1+2*-3}
+[eq 1+2*-3, -5]
 
 // Parentheses.
-{(a)}
-{(2)}
-{(1+2)*3}
+[eq (a), 2]
+[eq (2), 2]
+[eq (1+2)*3, 9]
 
 // Confusion with floating-point literal.
-{1e+2-1e-2}
+[eq 1e+2-1e-2, 99.99]
 
 // Error: 1:3-1:3 expected expression
 {-}
 
-// Error: 1:4-1:4 expected expression
-{1+}
+// Error: 1:8-1:8 expected expression
+[eq {1+}, 1]
 
-// Error: 1:4-1:4 expected expression
-{2*}
+// Error: 1:8-1:8 expected expression
+[eq {2*}, 2]
diff --git a/tests/lang/typ/headings.typ b/tests/lang/typ/headings.typ
index f62f6534..765d0377 100644
--- a/tests/lang/typ/headings.typ
+++ b/tests/lang/typ/headings.typ
@@ -1,38 +1,48 @@
 // Test different numbers of hashtags.
 
+// Valid levels.
 # One
 ### Three
 ###### Six
 
+// Too many hashtags.
 // Warning: 1:1-1:8 section depth should not exceed 6
 ####### Seven
 
 ---
 // Test heading vs. no heading.
 
+// Parsed as headings if at start of the context.
 /**/ # Heading
 {[## Heading]}
 [box][### Heading]
 
-\# No heading
-
+// Not at the start of the context.
 Text with # hashtag
 
-Nr#1
+// Escaped.
+\# No heading
 
+// Keyword.
 // Error: 1:1-1:6 unexpected invalid token
 #nope
 
+// Not parsed as a keyword, but neither as a heading.
+Nr#1
+
 ---
 // Heading continuation over linebreak.
 
+// Code blocks continue heading.
 # This {
-    "works"
+    "continues"
 }
 
+// Function call continues heading.
 # [box][
-    This
+    This,
 ] too
 
+// Without some kind of block, headings end at a line break.
 # This
-does not
+not
diff --git a/tests/lang/typ/let.typ b/tests/lang/typ/let.typ
index c7bba747..a966f243 100644
--- a/tests/lang/typ/let.typ
+++ b/tests/lang/typ/let.typ
@@ -1,20 +1,53 @@
+// Ref: false
+
 // Automatically initialized with `none`.
-#let x;
-{(x,)}
+#let x
+[eq x, none]
 
-// Can start with underscore.
-#let _y=1;
-{_y}
+// Initialized with `1`.
+#let y = 1;
+[eq y, 1]
 
-// Multiline.
-#let z = "world"
-    + " 🌏"; Hello, {z}!
+// Multiple bindings in one line.
+#let x = "a"; #let y = "b"; [eq x + y, "ab"]
 
+// No name.
 // Error: 1:6-1:7 expected identifier, found integer
-#let 1;
+#let 1
+
+---
+// Terminated with just a line break.
+#let v = "a"
+First
+[eq v, "a"]
+
+// Terminated with just a semicolon.
+#let v = "a"; Second
+[eq v, "a"]
+
+// Terminated with semicolon + line break.
+#let v = "a";
+Third
+[eq v, "a"]
+
+// Terminated by semicolon even though we are in a paren group.
+// Error: 2:22-2:22 expected expression
+// Error: 1:22-1:22 expected closing paren
+#let array = (1, 2 + ;Fourth
+[eq array, (1, 2)]
+
+// Not terminated.
+// Error: 1:14-1:20 expected semicolon or line break, found identifier
+#let v = "a" Unseen Fifth
+[eq v, "a"]
+
+// Not terminated by semicolon in template.
+#let v = [Hello; there]
 
-// Error: 4:1-4:3 unexpected identifier
-// Error: 3:4-3:9 unexpected identifier
-// Error: 3:1-3:1 expected semicolon
-#let x = ""
-Hi there
+// Not terminated by line break due to parens.
+#let x = (
+    1,
+    2,
+    3,
+)
+[eq x, (1, 2, 3)]
diff --git a/tests/lang/typ/linebreaks.typ b/tests/lang/typ/linebreaks.typ
new file mode 100644
index 00000000..ee2f453a
--- /dev/null
+++ b/tests/lang/typ/linebreaks.typ
@@ -0,0 +1,19 @@
+// Leading line break.
+\ Leading
+
+// Directly after word.
+Line\ Break
+
+// Spaces around.
+Line \ Break
+
+// Directly before word does not work.
+No \Break
+
+// Trailing before paragraph break.
+Paragraph 1 \
+
+Paragraph 2
+
+// Trailing before end of document.
+Paragraph 3 \
diff --git a/tests/lang/typ/nbsp.typ b/tests/lang/typ/nbsp.typ
new file mode 100644
index 00000000..b2f09950
--- /dev/null
+++ b/tests/lang/typ/nbsp.typ
@@ -0,0 +1,2 @@
+// Parsed correctly, but not actually doing anything at the moment.
+The non-breaking~space does not work.
diff --git a/tests/lang/typ/raw.typ b/tests/lang/typ/raw.typ
index 22eda139..2c0890ba 100644
--- a/tests/lang/typ/raw.typ
+++ b/tests/lang/typ/raw.typ
@@ -1,23 +1,28 @@
-The keyword ``rust let``.
+[font 8pt]
+
+// Typst syntax inside.
+`#let x = 1``[f 1]`
 
-`#let x = 1`
-`[f 1]`
+// Space between "rust" and "let" is trimmed.
+The keyword ``rust let``.
 
----
-[font 6pt]
+// Trimming depends on number backticks.
+<` untrimmed `> \
+<`` trimmed ``>
 
+// Multiline trimming.
 ``py
 import this
 
 def say_hi():
-    print("Hello World!")
+    print("Hi!")
 ``
 
----
+// Lots of backticks inside.
 ````
 ```backticks```
 ````
 
----
+// Unterminated.
 // Error: 2:1-2:1 expected backtick(s)
 `endless
diff --git a/tests/lang/typ/text.typ b/tests/lang/typ/text.typ
new file mode 100644
index 00000000..9c1e7977
--- /dev/null
+++ b/tests/lang/typ/text.typ
@@ -0,0 +1 @@
+Hello 🌏!
diff --git a/tests/lang/typ/values.typ b/tests/lang/typ/values.typ
index ce41fc43..51d0bd17 100644
--- a/tests/lang/typ/values.typ
+++ b/tests/lang/typ/values.typ
@@ -1,13 +1,24 @@
+// Test representation of values in the document.
+
 #let name = "Typst";
 #let ke-bab = "Kebab!";
 #let α = "Alpha";
 
+// Variables.
 {name} \
 {ke-bab} \
 {α} \
+
+// Error: 1:1-1:4 unknown variable
+{_}
+
+// Literal values.
 {none} (empty) \
 {true} \
 {false} \
+
+// Numerical values.
+{1} \
 {1.0e-4} \
 {3.15} \
 {1e-10} \
@@ -17,17 +28,16 @@
 {12e1pt} \
 {2.5rad} \
 {45deg} \
-{"hi"} \
-{"a\n[]\"\u{1F680}string"} \
-{#f7a20500} \
-{[*{"Hi"} [f 1]*]} \
-{{1}}
 
-// Error: 1:1-1:4 unknown variable
-{_} \
+// Colors.
+{#f7a20500} \
 
 // Error: 1:2-1:5 invalid color
 {#a5}
 
-// Error: 1:2-1:4 expected expression, found invalid token
-{1u}
+// Strings and escaping.
+{"hi"} \
+{"a\n[]\"\u{1F680}string"} \
+
+// Templates.
+{[*{"Hi"} [f 1]*]}
diff --git a/tests/typeset.rs b/tests/typeset.rs
index 10e6231e..fd5f4c81 100644
--- a/tests/typeset.rs
+++ b/tests/typeset.rs
@@ -1,7 +1,9 @@
+use std::cell::RefCell;
 use std::env;
 use std::ffi::OsStr;
 use std::fs;
 use std::path::Path;
+use std::rc::Rc;
 
 use fontdock::fs::FsIndex;
 use image::{GenericImageView, Rgba};
@@ -180,7 +182,8 @@ fn test_part(i: usize, src: &str, env: &mut Env) -> (bool, Vec<Frame>) {
     let (compare_ref, ref_diags) = parse_metadata(src, &map);
 
     let mut scope = library::new();
-    register_helpers(&mut scope);
+    let panicked = Rc::new(RefCell::new(false));
+    register_helpers(&mut scope, Rc::clone(&panicked));
 
     // We want to have "unbounded" pages, so we allow them to be infinitely
     // large and fit them to match their content.
@@ -201,6 +204,10 @@ fn test_part(i: usize, src: &str, env: &mut Env) -> (bool, Vec<Frame>) {
     diags.sort_by_key(|d| d.span);
 
     let mut ok = true;
+    if *panicked.borrow() {
+        ok = false;
+    }
+
     if diags != ref_diags {
         println!("  Subtest {} does not match expected diagnostics. ❌", i);
         ok = false;
@@ -259,7 +266,7 @@ fn parse_metadata(src: &str, map: &LineMap) -> (bool, SpanVec<Diag>) {
     (compare_ref, diags)
 }
 
-fn register_helpers(scope: &mut Scope) {
+fn register_helpers(scope: &mut Scope, panicked: Rc<RefCell<bool>>) {
     pub fn f(_: &mut EvalContext, args: &mut Args) -> Value {
         let (array, dict) = args.drain();
         let iter = array
@@ -281,7 +288,22 @@ fn register_helpers(scope: &mut Scope) {
         Value::Str(p.finish())
     }
 
+    let eq = move |ctx: &mut EvalContext, args: &mut Args| -> Value {
+        let lhs = args.require::<Value>(ctx, "left-hand side");
+        let rhs = args.require::<Value>(ctx, "right-hand side");
+        if lhs != rhs {
+            *panicked.borrow_mut() = true;
+            println!("  Assertion failed ❌");
+            println!("    left:  {:?}", lhs);
+            println!("    right: {:?}", rhs);
+            Value::Str(format!("(panic)"))
+        } else {
+            Value::None
+        }
+    };
+
     scope.set("f", ValueFunc::new("f", f));
+    scope.set("eq", ValueFunc::new("eq", eq));
 }
 
 fn print_diag(diag: &Spanned<Diag>, map: &LineMap) {