diff --git a/t/funcs.sh b/t/funcs.sh
new file mode 100644
index 0000000..d336424
--- /dev/null
+++ b/t/funcs.sh
@@ -0,0 +1,95 @@
+#!/bin/bash
+# vi: et sts=4 sw=4 ts=4
+
+echo_success() {
+    printf '[\033[1;32m%s\033[0;39m] %s' \
+        '  OK  ' \
+        "$*"
+}
+
+echo_failure() {
+    printf '[\033[1;31m%s\033[0;39m] %s' \
+        'FAILED' \
+        "$*"
+}
+
+echo_warning() {
+    printf '[\033[1;33m%s\033[0;39m] %s' \
+        'WARNING' \
+        "$*"
+}
+
+echo_passed() {
+    printf '[\033[1;33m%s\033[0;39m] %s' \
+        'PASSED' \
+        "$*"
+}
+
+assert_equals() {
+    local \
+        STARTER=$1 \
+        NEXT
+    shift 1
+    for NEXT; do
+        if [[ $STARTER != "$NEXT" ]]; then
+            echo_failure "$STARTER does not equal $NEXT"
+            echo
+            return 1
+        fi
+        echo_success "$STARTER equals $NEXT"
+        echo
+    done
+}
+
+assert_file_exists() {
+    local FN
+    for FN; do
+        if [[ ! -e $FN ]]; then
+            echo_failure "$FN does not exist"
+            echo
+            return 1
+        fi
+    done
+}
+
+assert_hardlinked() {
+    local \
+        STARTER=$1 \
+        NEXT
+    shift 1
+    for NEXT; do
+        if [[ ! $STARTER -ef $NEXT ]]; then
+            echo_failure "$STARTER is not hard-linked to $NEXT"
+            echo
+            return 1
+        fi
+        echo_success "$STARTER is hard-linked to $NEXT"
+        echo
+    done
+}
+
+assert_nothardlinked() {
+    local \
+        STARTER=$1 \
+        NEXT
+    shift 1
+    for NEXT; do
+        if [[ $STARTER -ef $NEXT ]]; then
+            echo_failure "$STARTER is hard-linked to $NEXT"
+            echo
+            return 1
+        fi
+        echo_success "$STARTER is not hard-linked to $NEXT"
+        echo
+    done
+}
+
+assert_older_than() {
+    if [[ $1 -ot $2 ]]; then
+        echo_failure "$1 is older than $2"
+        echo
+        return 1
+    fi
+    echo_success "$1 is not older than $2"
+    echo
+}
diff --git a/t/run.sh b/t/run.sh
new file mode 100755
index 0000000..a64e969
--- /dev/null
+++ b/t/run.sh
@@ -0,0 +1,118 @@
+#!/bin/bash
+# vi: et sts=4 sw=4 ts=4
+
+WORKDIR=${0%/*}
+. "$WORKDIR/funcs.sh"
+SCRIPT=$(realpath -- "$WORKDIR/../simplify_static_dir-main.pl")
+TAR=$(realpath -- "$WORKDIR/t.tar")
+TEMPDIR=$(mktemp -d -t "${0##*/}.XXXXXX")
+
+_prep_tar() {
+    rm -rf t &&
+    tar xf "$TAR"
+}
+cleanup() {
+    rm -rf -- "$TEMPDIR"
+}
+trap 'cleanup' EXIT
+
+test_normal_linkage() {
+    _prep_tar &&
+    $SCRIPT t || return 2
+    local -r \
+        FILE1=t/normal/foo/same \
+        FILE2=t/normal/same
+    assert_file_exists "$FILE1" "$FILE2" &&
+    assert_hardlinked "$FILE1" "$FILE2"
+}
+
+test_normal_nonlinkage() {
+    _prep_tar &&
+    $SCRIPT t || return 2
+    local -r \
+        FILE1=t/normal/foo/same \
+        FILE2=t/normal/not-same
+    assert_file_exists "$FILE1" "$FILE2" &&
+    assert_nothardlinked "$FILE1" "$FILE2"
+}
+
+test_sha1collision_nonlinkage() {
+    _prep_tar &&
+    $SCRIPT t || return 2
+    local -r \
+        FILE1=t/sha1-collision/shattered-1.pdf \
+        FILE2=t/sha1-collision/shattered-2.pdf
+    assert_file_exists "$FILE1" "$FILE2" &&
+    assert_nothardlinked "$FILE1" "$FILE2"
+}
+
+test_zero_size_nonlinkage() {
+    _prep_tar &&
+    $SCRIPT t || return 2
+    local -r \
+        FILE1=t/zero-size/empty1 \
+        FILE2=t/zero-size/empty2
+    assert_file_exists "$FILE1" "$FILE2" &&
+    assert_nothardlinked "$FILE1" "$FILE2"
+}
+
+test_link_counting() {
+    _prep_tar &&
+    $SCRIPT t || return 2
+    local -r FILES=(
+        t/link-counting/{most-links,second-most-links}
+    )
+    assert_file_exists "${FILES[@]}" &&
+    assert_hardlinked "${FILES[0]}" "${FILES[1]}"
+}
+
+test_timestamp_preservation() {
+    _prep_tar &&
+    $SCRIPT t || return 2
+    local -r \
+        FILE1=t/timestamp-preservation/newer-more-linked \
+        FILE2=t/timestamp-preservation/older-less-linked
+    assert_file_exists "$FILE1" "$FILE2" &&
+    assert_hardlinked "$FILE1" "$FILE2" &&
+    assert_older_than "$FILE2" "$FILE1"
+}
+
+test_freed_bytes() {
+    _prep_tar &&
+    local -r OUT=$($SCRIPT -f t/freed-bytes{,,} 2>&1 |tail -1)
+    local -r FILES=(
+        t/freed-bytes/{1,2,3,4}
+    )
+    assert_file_exists "${FILES[@]}" &&
+    assert_equals "$OUT" "freed 24 bytes (24 B)"
+}
+
+cd "$TEMPDIR" || exit
+TEST_COUNT=0
+TESTS_PASSED=0
+for TESTNAME in \
+    test_normal_linkage \
+    test_normal_nonlinkage \
+    test_sha1collision_nonlinkage \
+    test_zero_size_nonlinkage \
+    test_link_counting \
+    test_timestamp_preservation \
+    test_freed_bytes \
+    ; do
+
+    (( TEST_COUNT++ ))
+    if $TESTNAME; then
+        (( TESTS_PASSED++ ))
+    else
+        echo_failure "$TESTNAME failed"
+        echo
+    fi
+
+done
+
+cleanup
+
+printf '%d/%d tests passed\n' "$TESTS_PASSED" "$TEST_COUNT"
+if [[ $TESTS_PASSED -ne $TEST_COUNT ]]; then
+    exit 1
+fi
diff --git a/t/t.tar b/t/t.tar
new file mode 100644
index 0000000..fcf3d1f
Binary files /dev/null and b/t/t.tar differ