This test verifies that setting an empty suggested value removes/resets the shadow placeholder value.

Input before setting suggested values:
| <input>
|   id="test"
|   type="text"
|   value="initial value"
|   this.value="initial value"
|   <shadow:root>
|     <div>
|       "initial value"
| <br>
| "
"
| <input>
|   id="inputwithplaceholder"
|   placeholder="initial placeholder"
|   type="text"
|   this.value=""
|   <shadow:root>
|     <div>
|       id="placeholder"
|       pseudo="-webkit-input-placeholder"
|       style="display: block !important;"
|       shadow:pseudoId="-webkit-input-placeholder"
|       "initial placeholder"
|     <div>
| <br>
| "
"
| <textarea>
|   id="textarea"
|   this.value="initial value"
|   "initial value"
|   <shadow:root>
|     <div>
|       "initial value"
| <br>
| "
"
| <textarea>
|   id="textareaWithPlaceholder"
|   placeholder="initial placeholder"
|   this.value=""
|   <shadow:root>
|     <div>
|       id="placeholder"
|       pseudo="-webkit-input-placeholder"
|       style="display: block !important;"
|       shadow:pseudoId="-webkit-input-placeholder"
|       "initial placeholder"
|     <div>
|       <br>
|         aria-hidden="true"
|         id="textarea-placeholder-break"
| <br>
| "
"
| <select>
|   id="select"
|   <option>
|     "CA"
|     <shadow:root>
|       <span>
|         aria-hidden="true"
|         pseudo="-internal-option-label-container"
|         shadow:pseudoId="-internal-option-label-container"
|         "CA"
|       <slot>
|         pseudo="-internal-option-slot"
|         shadow:pseudoId="-internal-option-slot"
|   <option>
|     "TX"
|     <shadow:root>
|       <span>
|         aria-hidden="true"
|         pseudo="-internal-option-label-container"
|         shadow:pseudoId="-internal-option-label-container"
|         "TX"
|       <slot>
|         pseudo="-internal-option-slot"
|         shadow:pseudoId="-internal-option-slot"
|   <shadow:root>
|     <div>
|       aria-hidden="true"
|       pseudo="-internal-select-inner-element"
|       shadow:pseudoId="-internal-select-inner-element"
|       ""
|     <slot>
|       pseudo="-internal-select-button-slot"
|       shadow:pseudoId="-internal-select-button-slot"
|     <div>
|       popover="auto"
|       pseudo="picker(select)"
|       shadow:pseudoId="picker(select)"
|       <slot>
|         id="select-options"
|     <div>
|       popover="manual"
|       pseudo="-internal-select-autofill-preview"
|       shadow:pseudoId="-internal-select-autofill-preview"
|       <div>
|         pseudo="-internal-select-autofill-preview-text"
|         shadow:pseudoId="-internal-select-autofill-preview-text"
| "input.value: initial value"
| "internals.suggestedValue(input): "
| "inputWithPlaceholder.value: "
| "internals.suggestedValue(inputWithPlaceholder): "
| "textarea.value: initial value"
| "internals.suggestedValue(textarea): "
| "textareaWithPlaceholder.value: "
| "internals.suggestedValue(textareaWithPlaceholder): "
| "select.value: "
| "internals.suggestedValue(select): "

Input after setting suggestedValue:
| <input>
|   id="test"
|   type="text"
|   value="initial value"
|   this.value="initial value"
|   <shadow:root>
|     <div>
|       id="placeholder"
|       pseudo="-internal-input-suggested"
|       style="display: block !important; user-select: none !important;"
|       shadow:pseudoId="-internal-input-suggested"
|       "suggested value"
|     <div>
|       "initial value"
| <br>
| "
"
| <input>
|   id="inputwithplaceholder"
|   placeholder="initial placeholder"
|   type="text"
|   this.value=""
|   <shadow:root>
|     <div>
|       id="placeholder"
|       pseudo="-internal-input-suggested"
|       style="display: block !important; user-select: none !important;"
|       shadow:pseudoId="-internal-input-suggested"
|       "suggested value"
|     <div>
| <br>
| "
"
| <textarea>
|   id="textarea"
|   this.value="initial value"
|   "initial value"
|   <shadow:root>
|     <div>
|       id="placeholder"
|       pseudo="-internal-input-suggested"
|       style="display: block !important; user-select: none !important;"
|       shadow:pseudoId="-internal-input-suggested"
|       "suggested value"
|     <div>
|       "initial value"
| <br>
| "
"
| <textarea>
|   id="textareaWithPlaceholder"
|   placeholder="initial placeholder"
|   this.value=""
|   <shadow:root>
|     <div>
|       id="placeholder"
|       pseudo="-internal-input-suggested"
|       style="display: block !important; user-select: none !important;"
|       shadow:pseudoId="-internal-input-suggested"
|       "suggested value"
|     <div>
|       <br>
|         aria-hidden="true"
|         id="textarea-placeholder-break"
| <br>
| "
"
| <select>
|   id="select"
|   <option>
|     "CA"
|     <shadow:root>
|       <span>
|         aria-hidden="true"
|         pseudo="-internal-option-label-container"
|         shadow:pseudoId="-internal-option-label-container"
|         "CA"
|       <slot>
|         pseudo="-internal-option-slot"
|         shadow:pseudoId="-internal-option-slot"
|   <option>
|     "TX"
|     <shadow:root>
|       <span>
|         aria-hidden="true"
|         pseudo="-internal-option-label-container"
|         shadow:pseudoId="-internal-option-label-container"
|         "TX"
|       <slot>
|         pseudo="-internal-option-slot"
|         shadow:pseudoId="-internal-option-slot"
|   <shadow:root>
|     <div>
|       aria-hidden="true"
|       pseudo="-internal-select-inner-element"
|       shadow:pseudoId="-internal-select-inner-element"
|       ""
|     <slot>
|       pseudo="-internal-select-button-slot"
|       shadow:pseudoId="-internal-select-button-slot"
|     <div>
|       popover="auto"
|       pseudo="picker(select)"
|       shadow:pseudoId="picker(select)"
|       <slot>
|         id="select-options"
|     <div>
|       popover="manual"
|       pseudo="-internal-select-autofill-preview"
|       shadow:pseudoId="-internal-select-autofill-preview"
|       <div>
|         pseudo="-internal-select-autofill-preview-text"
|         shadow:pseudoId="-internal-select-autofill-preview-text"
|         "TX"
| "input.value: initial value"
| "internals.suggestedValue(input): "
| "inputWithPlaceholder.value: "
| "internals.suggestedValue(inputWithPlaceholder): "
| "textarea.value: initial value"
| "internals.suggestedValue(textarea): "
| "textareaWithPlaceholder.value: "
| "internals.suggestedValue(textareaWithPlaceholder): "
| "select.value: "
| "internals.suggestedValue(select): "
| "input.value: initial value"
| "internals.suggestedValue(input): suggested value"
| "inputWithPlaceholder.value: "
| "internals.suggestedValue(inputWithPlaceholder): suggested value"
| "textarea.value: initial value"
| "internals.suggestedValue(textarea): suggested value"
| "textareaWithPlaceholder.value: "
| "internals.suggestedValue(textareaWithPlaceholder): suggested value"
| "select.value: "
| "internals.suggestedValue(select): TX"

After resetting suggestedValue value:
| <input>
|   id="test"
|   type="text"
|   value="initial value"
|   this.value="initial value"
|   <shadow:root>
|     <div>
|       "initial value"
| <br>
| "
"
| <input>
|   id="inputwithplaceholder"
|   placeholder="initial placeholder"
|   type="text"
|   this.value=""
|   <shadow:root>
|     <div>
|       id="placeholder"
|       pseudo="-webkit-input-placeholder"
|       style="display: block !important;"
|       shadow:pseudoId="-webkit-input-placeholder"
|       "initial placeholder"
|     <div>
| <br>
| "
"
| <textarea>
|   id="textarea"
|   this.value="initial value"
|   "initial value"
|   <shadow:root>
|     <div>
|       "initial value"
| <br>
| "
"
| <textarea>
|   id="textareaWithPlaceholder"
|   placeholder="initial placeholder"
|   this.value=""
|   <shadow:root>
|     <div>
|       id="placeholder"
|       pseudo="-webkit-input-placeholder"
|       style="display: block !important;"
|       shadow:pseudoId="-webkit-input-placeholder"
|       "initial placeholder"
|     <div>
|       <br>
|         aria-hidden="true"
|         id="textarea-placeholder-break"
| <br>
| "
"
| <select>
|   id="select"
|   <option>
|     "CA"
|     <shadow:root>
|       <span>
|         aria-hidden="true"
|         pseudo="-internal-option-label-container"
|         shadow:pseudoId="-internal-option-label-container"
|         "CA"
|       <slot>
|         pseudo="-internal-option-slot"
|         shadow:pseudoId="-internal-option-slot"
|   <option>
|     "TX"
|     <shadow:root>
|       <span>
|         aria-hidden="true"
|         pseudo="-internal-option-label-container"
|         shadow:pseudoId="-internal-option-label-container"
|         "TX"
|       <slot>
|         pseudo="-internal-option-slot"
|         shadow:pseudoId="-internal-option-slot"
|   <shadow:root>
|     <div>
|       aria-hidden="true"
|       pseudo="-internal-select-inner-element"
|       shadow:pseudoId="-internal-select-inner-element"
|       ""
|     <slot>
|       pseudo="-internal-select-button-slot"
|       shadow:pseudoId="-internal-select-button-slot"
|     <div>
|       popover="auto"
|       pseudo="picker(select)"
|       shadow:pseudoId="picker(select)"
|       <slot>
|         id="select-options"
|     <div>
|       popover="manual"
|       pseudo="-internal-select-autofill-preview"
|       shadow:pseudoId="-internal-select-autofill-preview"
|       <div>
|         pseudo="-internal-select-autofill-preview-text"
|         shadow:pseudoId="-internal-select-autofill-preview-text"
| "input.value: initial value"
| "internals.suggestedValue(input): "
| "inputWithPlaceholder.value: "
| "internals.suggestedValue(inputWithPlaceholder): "
| "textarea.value: initial value"
| "internals.suggestedValue(textarea): "
| "textareaWithPlaceholder.value: "
| "internals.suggestedValue(textareaWithPlaceholder): "
| "select.value: "
| "internals.suggestedValue(select): "
| "input.value: initial value"
| "internals.suggestedValue(input): suggested value"
| "inputWithPlaceholder.value: "
| "internals.suggestedValue(inputWithPlaceholder): suggested value"
| "textarea.value: initial value"
| "internals.suggestedValue(textarea): suggested value"
| "textareaWithPlaceholder.value: "
| "internals.suggestedValue(textareaWithPlaceholder): suggested value"
| "select.value: "
| "internals.suggestedValue(select): TX"
| "input.value: initial value"
| "internals.suggestedValue(input): "
| "inputWithPlaceholder.value: "
| "internals.suggestedValue(inputWithPlaceholder): "
| "textarea.value: initial value"
| "internals.suggestedValue(textarea): "
| "textareaWithPlaceholder.value: "
| "internals.suggestedValue(textareaWithPlaceholder): "
| "select.value: "
| "internals.suggestedValue(select): "
| "PASS"