diff --git a/src/ARFFFiles.jl b/src/ARFFFiles.jl
index a45ba93..18a2fa8 100644
--- a/src/ARFFFiles.jl
+++ b/src/ARFFFiles.jl
@@ -255,7 +255,7 @@ function parse_type(data, pos, len, offset, opts1, opts2)
                 pos, fmt = parse_string(data, pos, len, offset, opts1, opts2)
                 return pos, ARFFDateType(fmt)
             else
-                return pos, ARFFDateType(fmt)
+                return pos, ARFFDateType()
             end
         elseif lstr == "relational"
             return pos, ARFFRelationalType()
@@ -406,7 +406,7 @@ function parse_javadateformat(java::AbstractString)
             write(io, c)
         end
     end
-    quoted && error("unclosed quote in date format: $(repr(arff))")
+    quoted && error("unclosed quote in date format: $(repr(java))")
     return DateFormat(String(take!(io)))
 end
 
diff --git a/test/load.jl b/test/load.jl
index 8393add..bd2ee9d 100644
--- a/test/load.jl
+++ b/test/load.jl
@@ -142,3 +142,200 @@ end
         ),
     )
 end
+
+@testitem "load missingcols strict" begin
+    using CategoricalArrays
+    using Tables
+    arff = """
+    @RELATION strict
+    @ATTRIBUTE num NUMERIC
+    @ATTRIBUTE str STRING
+    @DATA
+    % keep this line to cover comment skipping
+    1,"alpha"
+    ?,"beta"
+    """
+    table = ARFFFiles.load(NamedTuple, IOBuffer(arff); missingcols=false)
+    @test table.num[1] == 1.0
+    @test isnan(table.num[2])
+    @test table.str == ["alpha", "beta"]
+
+    reader = ARFFFiles.loadstreaming(IOBuffer(arff); missingcols=false)
+    chunk = ARFFFiles.readcolumns(reader; chunkbytes=nothing, maxbytes=nothing)
+    @test Tuple(Tables.schema(chunk).names) == (:num, :str)
+    nums = Tables.getcolumn(chunk, :num)
+    @test nums[1] == 1.0
+    @test isnan(nums[2])
+    close(reader)
+
+    arff_rel = """
+    @RELATION combos
+    @ATTRIBUTE cat {yes,no}
+    @ATTRIBUTE nested RELATIONAL
+        @ATTRIBUTE score NUMERIC
+    @END nested
+    @DATA
+    'yes','1.0'
+    'no','2.5'
+    """
+    reader = ARFFFiles.loadstreaming(IOBuffer(arff_rel); missingcols=false)
+    relchunk = ARFFFiles.readcolumns(reader)
+    cats = Tables.getcolumn(relchunk, :cat)
+    expected_cats = CategoricalArrays.CategoricalArray(["yes", "no"], levels = ["yes", "no"])
+    @test cats == expected_cats
+    nested = Tables.getcolumn(relchunk, :nested)
+    @test length(nested) == 2
+    @test all(x -> Tables.getcolumn(x, :score)[1] > 0, nested)
+    close(reader)
+end
+
+@testitem "load invalid data" begin
+    # strict missing string column should error
+    strict_missing = """
+    @RELATION strict-missing
+    @ATTRIBUTE str STRING
+    @DATA
+    ?
+    """
+    @test_throws ErrorException ARFFFiles.load(NamedTuple, IOBuffer(strict_missing); missingcols=false)
+
+    # invalid nominal choice
+    invalid_nominal = """
+    @RELATION cls
+    @ATTRIBUTE cls {yes,no}
+    @DATA
+    yes
+    maybe
+    """
+    err = try
+        ARFFFiles.load(NamedTuple, IOBuffer(invalid_nominal))
+        nothing
+    catch ex
+        ex
+    end
+    @test err !== nothing
+    @test occursin("Invalid nominal", sprint(showerror, err))
+
+    # sparse row with duplicate column index
+    dup_sparse = """
+    @RELATION dup
+    @ATTRIBUTE num NUMERIC
+    @ATTRIBUTE str STRING
+    @DATA
+    {0 1,0 2}
+    """
+    @test_throws ErrorException ARFFFiles.load(NamedTuple, IOBuffer(dup_sparse))
+
+    # sparse row omitting a required string column
+    strict_sparse = """
+    @RELATION strict-sparse
+    @ATTRIBUTE num NUMERIC
+    @ATTRIBUTE when DATE "yyyy-MM-dd'T'HH:mm:ss"
+    @DATA
+    {0 1}
+    """
+    @test_throws ErrorException ARFFFiles.load(NamedTuple, IOBuffer(strict_sparse); missingcols=false)
+
+    # sparse row missing closing brace
+    unclosed_sparse = """
+    @RELATION broken
+    @ATTRIBUTE num NUMERIC
+    @DATA
+    {0 1
+    """
+    @test_throws ErrorException ARFFFiles.load(NamedTuple, IOBuffer(unclosed_sparse))
+
+    # unsupported column type in header
+    struct DummyType <: ARFFFiles.ARFFType end
+    header = ARFFFiles.ARFFHeader("dummy", [ARFFFiles.ARFFAttribute("x", DummyType())])
+    @test_throws ErrorException ARFFFiles.loadstreaming(IOBuffer(""), header=header)
+end
+
+@testitem "sparse zero fill" begin
+    using CategoricalArrays
+    using Tables
+
+    arff = """
+    @RELATION fill
+    @ATTRIBUTE num NUMERIC
+    @ATTRIBUTE str STRING
+    @ATTRIBUTE cat {foo,bar}
+    @DATA
+    {0 1.0}
+    % inline comment to cover skip loop
+    {0 2.0,1 'hi',2 bar}
+    """
+
+    logbuf = IOBuffer()
+    logger = Base.CoreLogging.SimpleLogger(logbuf, Base.CoreLogging.Warn)
+    table = Base.CoreLogging.with_logger(logger) do
+        ARFFFiles.load(NamedTuple, IOBuffer(arff))
+    end
+    @test occursin("Value of string column 'str'", String(take!(logbuf)))
+    @test table.num == [1.0, 2.0]
+    @test table.str == ["", "hi"]
+    cats = table.cat
+    @test cats isa CategoricalArray{String,1,UInt32}
+    @test cats[1] == "foo"
+    @test cats[2] == "bar"
+    @test Tables.schema(table).names == (:num, :str, :cat)
+end
+
+@testitem "sparse non-missable date errors" begin
+    arff = """
+    @RELATION missing-date
+    @ATTRIBUTE num NUMERIC
+    @ATTRIBUTE when DATE "yyyy-MM-dd"
+    @DATA
+    {0 1.0}
+    """
+    err = try
+        ARFFFiles.load(NamedTuple, IOBuffer(arff))
+        nothing
+    catch ex
+        ex
+    end
+    @test err !== nothing
+    message = sprint(showerror, err)
+    @test occursin("Value of non-numeric column 'when'", message)
+end
+
+@testitem "readcolumns guard rails" begin
+    using ARFFFiles
+    using Dates
+
+    reader = ARFFFiles.loadstreaming(IOBuffer("""
+    @RELATION bogus
+    @ATTRIBUTE good NUMERIC
+    @DATA
+    1
+    """))
+    reader.colkinds[1] = :Z
+    @test_throws ErrorException ARFFFiles.readcolumns(reader)
+
+    sparse = """
+    @RELATION tiny
+    @ATTRIBUTE value NUMERIC
+    @DATA
+    {0 1.0}
+    """
+    legit = ARFFFiles.loadstreaming(IOBuffer(sparse))
+    chunk = collect(codeunits("1"))
+    opts = ARFFFiles.Parsing.options('\'')
+    @test_throws ErrorException ARFFFiles._readcolumns_readdatum(
+        legit,
+        Val(:Z),
+        chunk,
+        1,
+        length(chunk),
+        0,
+        1,
+        false,
+        1,
+        1,
+        opts,
+        opts,
+        Float64[],
+        nothing,
+    )
+end
diff --git a/test/parsing.jl b/test/parsing.jl
new file mode 100644
index 0000000..761388c
--- /dev/null
+++ b/test/parsing.jl
@@ -0,0 +1,124 @@
+@testitem "parse_header edge cases" begin
+    using ARFFFiles
+    using ARFFFiles: ARFFNominalType
+    using ARFFFiles.Parsing
+
+    # missing leading @ should trigger expect error
+    err = try
+        Parsing.parse_header(IOBuffer("@RELATION demo\nnot-a-directive\n"))
+        nothing
+    catch ex
+        ex
+    end
+    @test err !== nothing
+    @test occursin("expecting", sprint(showerror, err))
+
+    # unknown directive should trigger invalid header item
+    err = try
+        Parsing.parse_header(IOBuffer("@RELATION demo\n@FOO bar\n"))
+        nothing
+    catch ex
+        ex
+    end
+    @test err !== nothing
+    @test occursin("invalid header item", sprint(showerror, err))
+
+    # string parsing supports escaped quotes
+    single = Parsing.options('\'')
+    double = Parsing.options('"')
+    data = codeunits("'demo\\'s'")
+    _, relation = Parsing.parse_string(data, 1, length(data), 0, single, double)
+    @test relation == "demo's"
+    data = codeunits("'escaped\\'name'")
+    _, attrname = Parsing.parse_string(data, 1, length(data), 0, single, double)
+    @test attrname == "escaped'name"
+
+    # empty nominal list is accepted
+    data = codeunits("{}");
+    _, attrtype = Parsing.parse_type(data, 1, length(data), 0, single, double)
+    @test attrtype isa ARFFNominalType
+    @test isempty((attrtype::ARFFNominalType).classes)
+
+    # malformed escape sequences bubble the parse error
+    data = codeunits("'unfinished\\")
+    @test_throws ErrorException Parsing.parse_string(data, 1, length(data), 0, single, double)
+    @test_throws ErrorException Parsing.parse_escape("\\")
+end
+
+@testitem "parse_type validations" begin
+    using ARFFFiles.Parsing
+    using ARFFFiles
+    # invalid separators inside nominal braces
+    single = Parsing.options('\'')
+    double = Parsing.options('"')
+    data = codeunits("{yes no}")
+    err = try
+        Parsing.parse_type(data, 1, length(data), 0, single, double)
+        nothing
+    catch ex
+        ex
+    end
+    @test err !== nothing
+    @test occursin(",' or '}", sprint(showerror, err))
+
+    err = try
+        Parsing.parse_type(codeunits("bogus"), 1, length("bogus"), 0, single, double)
+        nothing
+    catch ex
+        ex
+    end
+    @test err !== nothing
+    @test occursin("invalid type", sprint(showerror, err))
+
+    # default DATE attributes fall back to the module default format
+    data = codeunits("date")
+    _, attrtype = Parsing.parse_type(data, 1, length(data), 0, single, double)
+    @test attrtype isa ARFFFiles.ARFFDateType
+    @test attrtype.format == ARFFFiles.ARFFDateType().format
+end
+
+@testitem "parse_javadateformat edge cases" begin
+    using ARFFFiles
+    using Dates
+
+    # doubled quotes emit a literal quote
+    fmt = ARFFFiles.parse_javadateformat("yy''MM")
+    @test Dates.format(Date(2020, 7, 1), fmt) == "20'07"
+
+    # unsupported format character
+    @test_throws ErrorException ARFFFiles.parse_javadateformat("Q")
+
+    # unclosed quote reports a descriptive error
+    err = try
+        ARFFFiles.parse_javadateformat("'open")
+        nothing
+    catch ex
+        ex
+    end
+    @test err isa ErrorException
+    message = sprint(showerror, err)
+    @test occursin("unclosed quote", message)
+    @test occursin("'open", message)
+end
+
+@testitem "parse_datum quote preference" begin
+    using ARFFFiles
+    using ARFFFiles: Parsing
+
+    single = Parsing.options('\'')
+    double = Parsing.options('"')
+
+    # double-quoted strings fall back from the single-quoted parser
+    data = codeunits("\"quoted\"")
+    res = Parsing.parse_datum(String, data, 1, length(data), single, double)
+    @test !Parsing.Parsers.invalid(res.code)
+    @test Parsing.Parsers.quoted(res.code)
+    @test Parsing.get_parsed_string(data, res) == "quoted"
+
+    # mismatched quotes prefer the single-quoted parse result
+    data = codeunits("'dangling\"")
+    res1 = Parsing.Parsers.xparse(String, data, 1, length(data), single)
+    res = Parsing.parse_datum(String, data, 1, length(data), single, double)
+    @test Parsing.Parsers.invalid(res.code)
+    @test res.code == res1.code
+end
diff --git a/test/save.jl b/test/save.jl
index 8a1c55a..ef09f43 100644
--- a/test/save.jl
+++ b/test/save.jl
@@ -46,3 +46,37 @@
         @test String(take!(io)) == expected
     end
 end
+
+@testitem "save edge cases" begin
+    using CategoricalArrays
+
+    io = IOBuffer()
+    ARFFFiles.write_datum(io, SubString("quoted", 1, 6))
+    @test String(take!(io)) == "'quoted'"
+
+    struct UInt8String <: AbstractString
+        data::Vector{UInt8}
+    end
+    Base.eltype(::Type{UInt8String}) = UInt8
+    Base.convert(::Type{String}, s::UInt8String) = String(s.data)
+    Base.String(s::UInt8String) = convert(String, s)
+    custom = UInt8String(codeunits("custom"))
+    io = IOBuffer()
+    ARFFFiles.write_datum(io, custom)
+    @test String(take!(io)) == "'custom'"
+
+    missing_only = (allmissing = [missing, missing],)
+    io = IOBuffer()
+    ARFFFiles.save(io, missing_only, relation = "missing", comment = "")
+    text = String(take!(io))
+    @test occursin("@ATTRIBUTE 'allmissing' {}", text)
+
+    cat_missing = (cats = CategoricalArray([missing, missing], levels = String[]),)
+    io = IOBuffer()
+    ARFFFiles.save(io, cat_missing, relation = "cats", comment = "")
+    text = String(take!(io))
+    @test occursin("@ATTRIBUTE 'cats' {}", text)
+
+    unsupported = (bad = ComplexF64[1 + 1im],)
+    @test_throws ErrorException ARFFFiles.save(IOBuffer(), unsupported, relation = "bad", comment = "")
+end