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Scryber.Core Test Coverage Analysis

Date: 2026-01-04 Analysis Scope: Unit test coverage gaps and missing test scenarios

Executive Summary

The scryber.core project has good coverage for layout and visual rendering but significant gaps in unit testing for core functionality, particularly:

  • Expression Engine Functions: 90+ functions with minimal direct unit testing
  • CSS Property Parsers: 118 parsers with limited parser-specific tests
  • Error Handling: Very few exception/error scenario tests
  • Font System: No dedicated font handling tests
  • Data Binding Edge Cases: Limited testing of error paths and edge cases

Table of Contents

  1. What IS Well Tested
  2. What is Missing or Under-Tested
  3. Priority Areas for Testing
  4. Specific Test Gap Examples
  5. Recommendations
  6. Conclusion

What IS Well Tested

1. Layout Engine (542+ test methods in Scryber.UnitLayouts)

Excellent Coverage:

  • ✅ Positioning (absolute, relative, fixed, floating, inline-block) - 197 tests
  • ✅ Tables (basic layout, sizing) - 33 tests
  • ✅ Breaks (page breaks, column breaks) - 11 tests
  • ✅ Text layout and whitespace - 38 tests
  • ✅ SVG rendering - 70 tests
  • ✅ Backgrounds and borders - 24 tests
  • ✅ Overflow handling - 32 tests
  • ✅ Panel/container layout - 16 tests
  • ✅ Header/footer positioning - 19 tests
  • ✅ Links and outlines - 3 tests

Files: Scryber.UnitLayouts/ (26 test files)

2. Drawing Primitives (Well tested)

Good Coverage:

  • ✅ PDFUnit, PDFPoint, PDFRect, PDFSize - dimension types
  • ✅ Color parsing and standard colors
  • ✅ Pen, Brush, Dash patterns
  • ✅ Transformation matrices
  • ✅ Graphics paths
  • ✅ Point arrays
  • ✅ Thickness calculations

Files: Scryber.UnitTest/Drawing/ (20+ test files)

3. PDF Native Types (Good coverage)

  • ✅ PDFArray, PDFDictionary, PDFName, PDFNumber, PDFReal
  • ✅ PDFString, PDFBoolean, PDFNull
  • ✅ PDFStream, PDFIndirectObject
  • ✅ PDFXRefTable

Files: Scryber.UnitTest/Native/ (11 test files)

4. Style System (Good coverage)

  • ✅ Style merging and cascading
  • ✅ Style stacks and priority
  • ✅ Selector matching and specificity
  • ✅ Individual style properties (font, text, background, border, etc.)
  • ✅ Style collections and groups

Files: Scryber.UnitTest/Styles/ (30+ test files)

5. HTML/CSS Parsing (Moderate coverage)

  • ✅ Basic HTML parsing (HtmlParsing_Tests.cs)
  • ✅ CSS parsing fundamentals (CssParsing_Tests.cs - 41 tests)
  • ✅ HTML transforms
  • ✅ Data images and gradients
  • ✅ SVG parsing

Files: Scryber.UnitTest/Html/ (8 test files)

6. Data Binding Basics (Moderate coverage)

  • ✅ Expression binding fundamentals
  • ✅ Handlebars helpers (each, with, if)
  • ✅ XML/HTML/JSON binding
  • ✅ Loop binding
  • ✅ Image binding
  • ✅ Controller binding

Files: Scryber.UnitTest/Binding/ (9 test files)

What is Missing or Under-Tested

1. CRITICAL: Expression Engine Functions (90+ functions, ~5-10% tested)

Implementation Location: Scryber.Expressions/Expressive/Functions/

Test Coverage: Only ~10-15 functions tested in IndividualExpressionTests.cs and scattered through binding tests

STRING FUNCTIONS (22 implementations, ~3 tested)

Missing tests for:

  • padLeft(), padRight() - String padding
  • trimStart(), trimEnd() - Partial trimming
  • indexOf() - String position finding
  • startsWith(), endsWith(), contains() - String testing
  • split() - String splitting
  • regexIsMatch(), regexMatches(), regexReplace() - Regex operations
  • toUpper(), toLower() - Case conversion
  • length() - String length
  • replace() - String replacement
  • join() - Array joining (only tested in complex scenarios)
  • format() (aka string()) - Formatting with various format strings
  • eval() - Dynamic expression evaluation

Tested: concat(), substring(), basic string operations in binding tests

MATHEMATICAL FUNCTIONS (23 implementations, 0 directly tested)

Missing tests for ALL:

  • abs(), ceiling(), floor(), round(), truncate() - Rounding functions
  • sqrt(), pow(), exp(), log(), log10() - Power/logarithm functions
  • sin(), cos(), tan(), asin(), acos(), atan() - Trigonometric functions
  • degrees(), radians() - Angle conversion
  • sign() - Sign determination
  • pi(), e() - Mathematical constants
  • random() - Random number generation
  • IEEERemainder() - IEEE remainder calculation

Tested: None directly (only used in complex expressions)

DATE/TIME FUNCTIONS (21 implementations, ~2 tested)

Missing tests for:

  • Add Functions (6): addDays(), addMonths(), addYears(), addHours(), addMinutes(), addSeconds(), addMilliseconds()
  • Between Functions (4): hoursBetween(), minutesBetween(), secondsBetween(), millisecondsBetween()
  • Extract Functions (9): yearOf(), monthOfYear(), dayOfMonth(), dayOfWeek(), hourOf(), minuteOf(), secondOf(), millisecondOf()
  • date() function with format strings

Tested: dayOfYear(), daysBetween() (partially)

STATISTICAL FUNCTIONS (5 implementations, ~3 tested)

Missing tests for:

  • mean() - Arithmetic mean
  • mode() - Most frequent value (only basic test exists)

Tested: average(), averageOf(), median() (basic tests)

COLLECTION/COALESCE FUNCTIONS (7 implementations, ~3 tested)

Missing comprehensive tests for:

  • eachOf() - Extract property from collection
  • selectWhere() - Filter collection
  • reverse() - Reverse array
  • collect() - Flatten/merge collections (only complex test exists)

Tested: sortBy(), firstWhere() (partial)

RELATIONAL FUNCTIONS (8 implementations, ~4 tested)

Missing tests for:

  • countOf() - Conditional counting
  • sumOf() - Sum of property values (used but not directly tested)
  • minOf(), maxOf() - Min/max of property values (partially tested)

Tested: count(), sum(), min(), max() (basic tests)

CONVERSION FUNCTIONS (8 implementations, ~2 tested)

Missing tests for:

  • bool() - Boolean conversion
  • long() - Long integer conversion
  • decimal(), double() - Decimal conversions
  • typeof() - Type information
  • date() - Date parsing with various formats

Tested: integer(), string() (partially)

LOGICAL FUNCTIONS (4 implementations, ~2 tested)

Missing tests for:

  • index() - Index-based access
  • Complex if() scenarios with nested expressions

Tested: ifError(), in(), basic if()

CSS FUNCTIONS (2 implementations, 0 tested)

Missing tests for:

  • calc() - CSS calc() expression generation
  • var() - CSS variable reference

2. CSS PROPERTY PARSERS (118 parsers, minimal parser-specific tests)

Implementation Location: Scryber.Styles/Styles/Parsing/Typed/

Test Coverage: CssParsing_Tests.cs has 41 tests, but most test CSS integration, not individual parser edge cases

Missing Parser-Specific Tests:

Box Model Parsers (24 parsers):

  • Margin parsers (8): top, right, bottom, left, all, inline-start, inline-end, inline-both
  • Padding parsers (8): top, right, bottom, left, all, inline-start, inline-end, inline-both
  • Border parsers (8): border-width, border-style, border-color, border-radius, border-top/right/bottom/left
  • Min/max width/height (4)

Typography Parsers (12 parsers):

  • font, font-family, font-size, font-weight, font-style, font-stretch
  • line-height, letter-spacing, word-spacing
  • text-align, text-decoration, vertical-align

Background Parsers (8 parsers):

  • background, background-color, background-image
  • background-position, background-position-x, background-position-y
  • background-repeat, background-size

Positioning Parsers (7 parsers):

  • position, top, right, bottom, left
  • float, display

Page Break Parsers (6 parsers):

  • page-break-before, page-break-after, page-break-inside
  • break-before, break-after, break-inside

Column Parsers (6 parsers):

  • column-count, column-width, column-gap, column-span
  • column-break-before, column-break-after, column-break-inside

Hyphenation Parsers (5 parsers):

  • hyphens, hyphenate-min-length
  • hyphens-min-before, hyphens-min-after
  • hyphenate-limits

SVG-Specific Parsers (10 parsers):

  • fill, fill-color, fill-opacity
  • stroke, stroke-color, stroke-width, stroke-opacity
  • stroke-dash, stroke-dash-offset
  • stroke-line-cap, stroke-line-join
  • paint-order, dominant-baseline, text-anchor

List Style Parsers (8 parsers):

  • list-style, list-style-type
  • list-item-alignment, list-item-concatenation
  • list-item-group, list-item-inset
  • list-item-prefix, list-item-postfix

Other Parsers (12 parsers):

  • overflow, overflow-x, overflow-y, overflow-action
  • white-space, content
  • counter-reset, counter-increment
  • opacity, transform
  • page, page-size

Edge Cases Missing Tests:

  • Invalid CSS values for each property
  • Boundary values (0, negative, max values)
  • Unit conversions (pt, px, em, rem, %, mm, cm, in)
  • Color formats (hex, rgb, rgba, hsl, hsla, named colors, transparent)
  • Shorthand property expansion (margin: 10pt 20pt, border: 1pt solid red)
  • Inheritance and cascading edge cases
  • CSS variable substitution edge cases
  • calc() expression parsing edge cases

3. TABLE LAYOUT COMPLEX SCENARIOS (Limited coverage)

Current Coverage: 33 tests in Table_Tests.cs

Missing Tests:

Colspan edge cases:

  • Colspan spanning multiple columns with varying widths
  • Colspan at end of row
  • Colspan with auto-width columns
  • Nested tables with colspan

Rowspan edge cases:

  • Rowspan across page breaks
  • Rowspan with varying row heights
  • Complex rowspan + colspan combinations
  • Rowspan in thead/tbody/tfoot

Table layout algorithms:

  • Auto table layout algorithm
  • Fixed table layout algorithm
  • Table width calculation with percentage columns
  • Min-width/max-width constraints on tables

Table headers/footers:

  • Thead repeating on multiple pages
  • Tfoot appearing on last page only
  • Complex thead/tfoot with merged cells

Table borders:

  • Border collapse algorithm
  • Border-spacing with various values
  • Borders with rowspan/colspan cells

Table overflow:

  • Wide tables exceeding page width
  • Table wrapping behavior
  • Horizontal scrolling scenarios

4. FONT HANDLING (No dedicated tests)

Current Coverage: FontMetrics_Test.cs, PDFFont_Test.cs, FontSelector_Test.cs exist but limited

Missing Tests:

Font loading:

  • TrueType font loading and validation
  • OpenType font loading
  • Font fallback chain
  • Missing font handling
  • Font embedding vs. subsetting

Font metrics:

  • Ascent, descent, line height calculations
  • Character width measurements
  • Kerning pair handling
  • Ligature handling

Font matching:

  • Font family fallback (e.g., "Arial, Helvetica, sans-serif")
  • Font weight matching (100-900)
  • Font style matching (normal, italic, oblique)
  • Font stretch matching

Unicode handling:

  • Multi-byte character support
  • Right-to-left text
  • Complex scripts (Arabic, Hindi, Thai)
  • Emoji rendering

Web fonts:

  • Google Fonts loading
  • @font-face CSS rule parsing
  • Font format detection (ttf, otf, woff, woff2)
  • Font loading errors and fallbacks

5. IMAGE PROCESSING (Minimal tests)

Current Coverage: ImageLoad_Tests.cs, ImageType_Tests.cs have 7-8 exception tests

Missing Tests:

Image format handling:

  • JPEG loading (quality, progressive, EXIF)
  • PNG loading (transparency, interlacing, color depths)
  • GIF loading (animation, transparency)
  • TIFF loading (multi-page, compression)

Data URL images:

  • Base64 encoding/decoding
  • Various image formats in data URLs
  • Large data URL handling
  • Invalid data URL handling

Image sizing:

  • Aspect ratio preservation
  • Image scaling algorithms
  • Max-width/max-height constraints
  • Object-fit CSS property

Image optimization:

  • Image compression
  • Image resampling
  • Color space conversion
  • JPEG pass-through optimization

Image errors:

  • Missing images
  • Corrupt image files
  • Unsupported formats
  • Network errors loading remote images
  • Timeout handling

6. ERROR HANDLING AND EDGE CASES (Very limited)

Current Coverage: Only 174 occurrences of try/catch across 35 files, ZERO tests using ExpectedException or Assert.Throws

Missing Error Scenario Tests:

Expression Evaluation Errors:

  • Division by zero in expressions
  • Type mismatch errors (string + number)
  • Undefined variable access
  • Null reference in expressions
  • Array index out of bounds
  • Function parameter count mismatch
  • Recursive expression evaluation
  • Stack overflow in nested expressions

CSS Parsing Errors:

  • Malformed CSS syntax
  • Invalid property values
  • Circular @import references
  • Missing semicolons
  • Unclosed brackets/quotes
  • Invalid selectors
  • CSS variable circular references

Data Binding Errors:

  • Missing data properties
  • Type conversion failures
  • Circular references in data
  • Null data objects
  • Invalid JSON
  • XML parsing errors
  • SQL query errors
  • Network timeouts

Layout Errors:

  • Infinite layout loops
  • Negative dimensions
  • Extremely large content
  • Invalid positioning values
  • Circular containment
  • Missing required properties

PDF Generation Errors:

  • Disk full during write
  • Stream write errors
  • Encoding errors
  • Security/encryption errors
  • Malformed PDF structure
  • Resource limit exceeded

Font Errors:

  • Missing font files
  • Corrupt font data
  • Unsupported font formats
  • Font embedding failures
  • Character not in font

Image Errors:

  • Out of memory with large images
  • Corrupt image data
  • Unsupported formats
  • Network failures
  • Access denied errors

7. DATA BINDING EDGE CASES (Limited coverage)

Current Coverage: 9 binding test files, mostly happy path scenarios

Missing Tests:

Complex Object Graphs:

  • Deeply nested objects (10+ levels)
  • Circular references detection
  • Very large arrays (10,000+ items)
  • Sparse arrays
  • Objects with null properties
  • Mixed type arrays

Expression Edge Cases:

  • Very long expressions (1000+ chars)
  • Deeply nested function calls
  • Complex operator precedence
  • Whitespace handling in expressions
  • Unicode in expressions
  • Special characters in property names

Handlebars Edge Cases:

  • Nested {{#each}} loops (3+ levels)
  • {{#each}} with empty arrays
  • {{#each}} with null data
  • {{#with}} with missing properties
  • {{#if}} with complex conditions
  • Combining multiple helpers
  • Helper parameter edge cases

Context Navigation:

  • Multiple levels of ../ parent access
  • Context switching in nested templates
  • Variable shadowing
  • Scope resolution with same-named properties

Performance Scenarios:

  • Binding 1000+ elements
  • Expression evaluation performance
  • Large data set pagination
  • Memory usage with large documents

8. HYPHENATION (No comprehensive tests)

Current Coverage: Hyphenation_Test.cs exists (1 file)

Missing Tests:

  • Hyphenation dictionary loading
  • Language-specific hyphenation rules
  • Min-word-length before hyphenation
  • Min-characters before/after hyphen
  • Hyphenation limits (max consecutive lines)
  • Custom hyphenation patterns
  • Soft hyphen (­) handling
  • Non-breaking hyphen handling
  • Hyphenation in different languages
  • Hyphenation with right-to-left text

9. PAGE BREAKS AND LAYOUT FLOW (Partial coverage)

Current Coverage: Breaks_Tests.cs (11 tests)

Missing Tests:

Orphans and widows:

  • Orphan control (min lines at end of page)
  • Widow control (min lines at start of page)
  • Orphan/widow with tables
  • Orphan/widow with lists

Page break avoidance:

  • page-break-inside: avoid edge cases
  • Keep-together scenarios
  • Unbreakable content exceeding page height
  • Forced breaks vs. natural breaks

Column breaks:

  • Multi-column layout balancing
  • Column break with spanning elements
  • Column fill (auto vs. balance)

Complex break scenarios:

  • Nested break contexts
  • Breaks in positioned elements
  • Breaks in floated elements
  • Breaks in absolutely positioned content

10. SVG ADVANCED FEATURES (Partial coverage)

Current Coverage: 70 tests in SVG_Tests.cs, SVGComponent_Tests.cs

Missing Tests:

SVG Filters:

  • Blur filters
  • Drop shadows
  • Color matrix filters
  • Composite filters

SVG Gradients Advanced:

  • Gradient transforms
  • Gradient units (objectBoundingBox vs userSpaceOnUse)
  • Gradient spread methods (pad, reflect, repeat)

SVG Clipping and Masking:

  • clipPath elements
  • Mask elements
  • Complex clipping shapes

SVG Symbols and Defs:

  • Symbol reuse
  • Defs reference handling
  • Use element with transforms

SVG Text Advanced:

  • Text on path
  • Text spans with varying styles
  • Text rotation
  • Text anchor positions

Priority Areas for Testing

HIGH PRIORITY (Critical for reliability)

1. Expression Functions Unit Tests

  • Create comprehensive unit tests for each of the 90+ functions
  • Test with various data types (null, undefined, empty, boundary values)
  • Test error scenarios (invalid parameters, type mismatches)
  • Estimated: 300-500 test methods needed

2. Error Handling Tests

  • Add tests for all exception paths
  • Test invalid input handling across all components
  • Test resource failure scenarios (file not found, network errors)
  • Estimated: 100-200 test methods needed

3. CSS Parser Edge Case Tests

  • Test each of the 118 parsers with invalid inputs
  • Test boundary values and unit conversions
  • Test shorthand property expansion
  • Estimated: 200-300 test methods needed

4. Font Handling Tests

  • Test font loading (TrueType, OpenType, Web fonts)
  • Test font fallback chains
  • Test missing font handling
  • Test font metrics and measurements
  • Estimated: 50-100 test methods needed

MEDIUM PRIORITY (Important for robustness)

5. Table Layout Complex Scenarios

  • Colspan/rowspan edge cases
  • Table overflow and wrapping
  • Page breaks in tables
  • Border collapse algorithm
  • Estimated: 50-100 test methods needed

6. Image Processing Tests

  • Test each image format with various edge cases
  • Test data URL handling
  • Test image sizing and scaling
  • Test error scenarios
  • Estimated: 40-80 test methods needed

7. Data Binding Edge Cases

  • Large and complex object graphs
  • Circular reference detection
  • Performance tests with large datasets
  • Nested template scenarios
  • Estimated: 50-100 test methods needed

8. Hyphenation Tests

  • Language-specific rules
  • Hyphenation limits and boundaries
  • Custom patterns
  • Estimated: 20-40 test methods needed

LOW PRIORITY (Nice to have)

9. SVG Advanced Features

  • Filters, clipping, masking
  • Advanced text features
  • Estimated: 30-60 test methods needed

10. Page Break Advanced Scenarios

  • Orphan/widow control
  • Complex nesting scenarios
  • Estimated: 20-40 test methods needed

Specific Test Gap Examples

Example 1: String Function - padLeft()

Implementation: Scryber.Expressions/Expressive/Functions/String/PadLeftFunction.cs Tests: None found Needed Tests:

[TestMethod]
public void PadLeft_WithDefaultChar_PadsCorrectly()
{
    // Test: padLeft('test', 10) should return '      test'
}

[TestMethod]
public void PadLeft_WithCustomChar_PadsCorrectly()
{
    // Test: padLeft('test', 10, '0') should return '000000test'
}

[TestMethod]
public void PadLeft_WithNegativeLength_ThrowsException()
{
    // Test: padLeft('test', -1) should throw
}

[TestMethod]
public void PadLeft_WithNullString_HandlesGracefully()
{
    // Test: padLeft(null, 10) behavior
}

Example 2: Mathematical Function - sqrt()

Implementation: Scryber.Expressions/Expressive/Functions/Mathematical/SqrtFunction.cs Tests: None found Needed Tests:

[TestMethod]
public void Sqrt_OfPositiveNumber_ReturnsCorrectValue()
{
    // Test: sqrt(16) should return 4
}

[TestMethod]
public void Sqrt_OfZero_ReturnsZero()
{
    // Test: sqrt(0) should return 0
}

[TestMethod]
public void Sqrt_OfNegativeNumber_ThrowsOrReturnsNaN()
{
    // Test: sqrt(-1) behavior
}

[TestMethod]
public void Sqrt_OfNonNumeric_ThrowsException()
{
    // Test: sqrt('text') should throw
}

Example 3: CSS Parser - CSSBorderRadiusParser

Implementation: Scryber.Styles/Styles/Parsing/Typed/CSSBorderRadiusParser.cs Tests: Minimal in CssParsing_Tests.cs Needed Tests:

[TestMethod]
public void BorderRadius_SingleValue_AppliesAllCorners()
{
    // Test: border-radius: 10pt
}

[TestMethod]
public void BorderRadius_TwoValues_AppliesTopBottomAndLeftRight()
{
    // Test: border-radius: 10pt 20pt
}

[TestMethod]
public void BorderRadius_FourValues_AppliesEachCorner()
{
    // Test: border-radius: 10pt 20pt 30pt 40pt
}

[TestMethod]
public void BorderRadius_WithSlash_AppliesElliptical()
{
    // Test: border-radius: 10pt / 20pt
}

[TestMethod]
public void BorderRadius_InvalidValue_ThrowsOrIgnores()
{
    // Test: border-radius: invalid
}

Example 4: Table Colspan Edge Case

Implementation: Scryber.Components/PDF/Layout/LayoutEngineTable.cs Tests: Basic colspan test exists Needed Tests:

[TestMethod]
public void Table_ColspanExceedingColumns_ThrowsOrHandles()
{
    // Test: colspan="5" in 3-column table
}

[TestMethod]
public void Table_ColspanWithAutoWidth_DistributesCorrectly()
{
    // Test: colspan cells with auto-width siblings
}

[TestMethod]
public void Table_ColspanAcrossPageBreak_BreaksCorrectly()
{
    // Test: large colspan cell spanning page break
}

[TestMethod]
public void Table_ColspanAndRowspanCombined_LayoutsCorrectly()
{
    // Test: cell with both colspan and rowspan
}

Example 5: Error Handling - Division by Zero

Implementation: Throughout expression engine Tests: None found using Assert.Throws or ExpectedException Needed Tests:

[TestMethod]
[ExpectedException(typeof(DivideByZeroException))]
public void Expression_DivisionByZero_ThrowsException()
{
    // Test: {{10 / 0}} should throw
}

[TestMethod]
public void Expression_DivisionByZeroInFunction_HandlesGracefully()
{
    // Test: {{if(true, 10/0, 5)}} error handling
}

Example 6: Font Fallback

Implementation: Scryber.Components/Components/DocumentFontMatcher.cs Tests: Limited in FontSelector_Test.cs Needed Tests:

[TestMethod]
public void FontMatcher_WithMissingFont_UsesFirstFallback()
{
    // Test: "NonExistentFont, Arial, sans-serif" uses Arial
}

[TestMethod]
public void FontMatcher_WithAllMissingFonts_UsesDefaultFont()
{
    // Test: "Font1, Font2, Font3" all missing
}

[TestMethod]
public void FontMatcher_WithWeightNotAvailable_UsesClosestWeight()
{
    // Test: font-weight: 650 with only 400, 700 available
}

Recommendations

1. Create Dedicated Test Projects

Consider splitting tests into more focused projects:

  • Scryber.Expressions.UnitTests - For all 90+ expression functions
  • Scryber.Styles.UnitTests - For CSS parser edge cases
  • Scryber.ErrorHandling.Tests - For exception scenarios
  • Scryber.Font.UnitTests - For font system tests

2. Implement Test Data Builders

Create builder pattern classes for complex test scenarios:

var table = new TableBuilder()
    .WithColumns(3)
    .AddRow(row => row.AddCell(colspan: 2).AddCell())
    .AddRow(row => row.AddCell(rowspan: 2).AddCell().AddCell())
    .Build();

3. Add Property-Based Testing

Use FsCheck or similar for property-based testing:

  • CSS parser with random valid/invalid inputs
  • Expression evaluation with random expressions
  • Layout engine with random dimensions

4. Performance Benchmarks

Add performance tests for:

  • Large document generation (100+ pages)
  • Complex table layouts (1000+ rows)
  • Expression evaluation performance (1000+ evaluations)
  • Image processing with large images

5. Integration Test Suite

Create comprehensive integration tests for:

  • End-to-end document generation scenarios
  • Multi-page documents with headers/footers
  • Complex data binding with real-world data
  • Error recovery scenarios

Conclusion

Scryber.core has excellent layout and visual rendering test coverage but significant gaps in unit testing for core functionality. The most critical missing areas are:

  1. Expression Engine Functions (90+ functions, <10% tested)
  2. CSS Property Parsers (118 parsers, minimal edge case testing)
  3. Error Handling (Zero tests using Assert.Throws/ExpectedException)
  4. Font System (No dedicated font handling tests)
  5. Complex Table Scenarios (Colspan/rowspan edge cases)
  6. Image Processing (Limited format-specific tests)
  7. Overflow Integration Tests (Checks for overflowing content within columns and pages - using css)

Priority: Focus on adding comprehensive unit tests for the Expression Engine and implementing systematic error scenario testing across all components. These are the highest-risk areas that could lead to production issues.

Estimated Test Effort: 1000-2000 additional test methods needed to achieve comprehensive coverage of missing areas.

Summary Statistics

Category Current State Missing Tests Priority
Expression Functions ~10% tested 300-500 tests HIGH
Error Handling 0 exception tests 100-200 tests HIGH
CSS Parsers Integration only 200-300 tests HIGH
Font Handling Limited 50-100 tests HIGH
Table Complex Scenarios Basic only 50-100 tests MEDIUM
Image Processing Minimal 40-80 tests MEDIUM
Data Binding Edge Cases Happy path only 50-100 tests MEDIUM
Hyphenation 1 file 20-40 tests MEDIUM
SVG Advanced Partial 30-60 tests LOW
Page Breaks Advanced Partial 20-40 tests LOW

Total Estimated Missing Tests: 1000-2000 test methods

This analysis was generated on 2026-01-04 through comprehensive codebase exploration and test coverage review.